Superoxide dismutases (SOD) are ubiquitous metalloenzymes that catalyze the disproportion of superoxide to peroxide and molecular oxygen through alternate oxidation and reduction of their metal ions. In general, SODs are classified into four forms by their catalytic metals namely; FeSOD, MnSOD, Cu/ZnSOD and NiSOD. In addition, a cambialistic form that uses Fe/Mn in its active site also exists. Cyanobacteria, the oxygen evolving photosynthetic prokaryotes, produce reactive oxygen species that can damage cellular components leading to cell death. Thus, the co-evolution of an antioxidant system was necessary for the survival of photosynthetic organisms with SOD as the initial enzyme evolved to alleviate the toxic effect. Cyanobacteria represent the first oxygenic photoautotrophs and their SOD sequences available in the databases lack clear annotation. Hence, the present study focuses on structure and sequence pattern of subsets of cyanobacterial superoxide dismutases.
Result
The sequence conservation and structural analysis of Fe (Thermosynechococcus elongatus BP1) and MnSOD (Anabaena sp. PCC7120) reveal the sharing of N and C terminal domains. At the C terminal domain, the metal binding motif in cyanoprokaryotes is DVWEHAYY while it is D-X-[WF]-E-H-[STA]-[FY]-[FY] in other pro- and eukaryotes. The cyanobacterial FeSOD differs from MnSOD at least in three ways viz. (i) FeSOD has a metal specific signature F184X3A188Q189.......T280......F/Y303 while, in Mn it is R184X3G188G189......G280......W303, (ii) aspartate ligand forms a hydrogen bond from the active site with the outer sphere residue of W243 in Fe where as it is Q262 in MnSOD; and (iii) two unique lysine residues at positions 201 and 255 with a photosynthetic role, found only in FeSOD. Further, most of the cyanobacterial Mn metalloforms have a specific transmembrane hydrophobic pocket that distinguishes FeSOD from Mn isoform. Cyanobacterial Cu/ZnSOD has a copper domain and two different signatures G-F-H-[ILV]-H-x-[NGT]-[GPDA]-[SQK]-C and G-[GA]-G-G-[AEG]-R-[FIL]-[AG]-C-G, while Ni isoform has an nickel containing SOD domain containing a Ni-hook HCDGPCVYDPA.
Conclusion
The present analysis unravels the ambiguity among cyanobacterial SOD isoforms. NiSOD is the only SOD found in lower forms; whereas, Fe and Mn occupy the higher orders of cyanobacteria. In conclusion, cyanobacteria harbor either Ni alone or a combination of Fe and Ni or Fe and Mn as their catalytic active metal while Cu/Zn is rare.
Background
Superoxide dismutases (SODs, E.C. 1.15.1.1) are the superfamily of metalloenzymes that dismutases the highly toxic and reactive superoxide radical (O2-, by-product of aerobic metabolism) through a cyclic oxidation-reduction ('ping-pon g') mechanism. As described by McCord and Fridovich [1], it is the first line of defense to alleviate oxidative stress virtually in all living organisms that survive in oxic environment.
The evolutionary trajectory has favored SOD as a ubiquitous enzyme in multiple forms within a single organism or cell, indicating a fail-safe redundancy that emphasizes the importance of this family of enzymes against reactive oxygen species (ROS). Based on metal cofactors, four known (canonical) isoforms viz., iron (Fe), manganese (Mn), copper/zinc (Cu/Zn) and nickel (Ni) SODs have been identified. In general, SODs have a strict metal binding specificity for enzymatic activities with the exception of a class of enzymes which show enzymatic activity regardless of whether Fe or Mn is bound at the active site; these are known as cambialistic forms [2–5].
Cyanoprokaryotes are oxygen evolving photosynthetic organisms occupying a crucial position between pro- and eukaryotes. They are considered to be primeval having evolved about 3.2 billion years ago [6]. In addition, they succeeded in linking photosynthetic electron flow from water as the photoreductant through an oxygen-evolving complex at the high-potential side of the newly elaborated photosystem II, which is thought to have originated from a uniform primordial photosystem by gene duplication [7]. The resultant tandem operation of two photosystems is now known as oxygenic or plant-type photosynthesis [8]. This marked the turning point in the evolution of earth, opening up the era of an aerobic, oxygen-containing biosphere and SOD is found to play a critical role in mitigating the toxic effect of superoxide ion. The first implication on the protective role of cyanobacterial SOD in photo-oxidative damage was shown in Anacystis nidulans [9]. Subsequently, several studies on protective role of SODs of cyanobacteria in response to various physiological processes/stresses like photosynthesis [10], desiccation [11, 12], chilling [13], nitrogen starvation [14] and with azo dyes (unpublished) have been reported.
Metal preferences in Fe and MnSODs have been well documented in both pro- and eukaryotic forms [15–17]. However, no information is available on distinguishing the canonical isoforms of cyanobacteria. Hence, the present study focuses on structure and sequence pattern of subsets of cyanobacterial SODs to explore the possibility of solving the ambiguity.
Results and Discussion
For the survival of cyanobacteria with oxygenic photosynthesis, the selection pressure led to the evolution of SODs as the first antioxidant arsenal against nascent oxygen species. Studies on cyanobacterial SODs would serve as a window into the past and present evolutionary events of these primitive phototrophs.
On comparison, the canonical isoforms of SOD, Fe and MnSOD's are structurally distinct from Cu/Zn and NiSOD. Both Fe and MnSOD are typically homodimers or tetramers (Fig 1A,C) sharing identical metal chelating residues at the active site with a high degree of sequence and structural homology except for slight differences in amino acid residues. For instance, the amino acid range in cyanobacterial FeSOD is 199–229 residues with a molecular weight of 21–25 KDa, whereas in MnSOD, it is 200–316 amino acids with a molecular weight of 22–34 KDa.
Figure 1
Structure of Fe and MnSOD. Structures are visualized using WebLab ViewerLite 4.2 software. Catalytically essential aspartate or histidine residues are represented in ball and stick mode binding the active metal (yellow) is shown to identify the location of the active site. Protein database codes are given in parentheses: (i) FeSOD (PDB 1gv3); (ii) MnSOD (PDB 1my6). (A) FeSOD of T.elongatus BP-1 dimers are distinguished by colour (violet and slate), and structures are represented with the active site (yellow) of subunit. (B) Monomeric subunit of FeSOD represents an N terminal (green) and a C- terminal (red). Similarly (C) represents dimer structure of Anabaena sp. MnSOD in pink and green with active site highlighted in yellow. (D) Monomeric MnSOD showing the N-terminal residues in blue and C-terminal in pink with metal binding ligands. The transmembrane hydrophobic pocket specific for MnSOD is highlighted in red (D).
Both SODs revealed a common topology with all α N-terminal (Pfam:PF00081) and a α/β C terminal domains (Pfam:PF02777) (Fig 1B,D). The sequence pattern for Fe and MnSODs of eukaryotes and other non-cyanobacterial prokaryotes is D-X-[WF]-E-H-[STA]-[FY]-[FY] [18]; whereas, the analysis of the sequence conservation in cyanobacteria (based on available data) showed a specific motif DVWEHAYY [D282-Y289, based on Fig 2]. This motif extends between the second α-helix and the first β-sheet of the C-terminal domain in both the SOD's. The highly conserved residues aspartate D282 and histidine H286, a constituent of the motif are the metal binding ligands. In addition, glutamic acid E285 and tyrosine Y289 form a dimer surface spanning the interface and bridging the active sites between the opposite halves of each subunit, see Figure 2 (For full image, please see Additional file 1).
Figure 2
This figure shows the lower quartile of protein sequence alignment of Fe and MnSODs in cyanobacteria. The highly conserved metal specific residues are highlighted in red for Fe and green for MnSODs. Residues involved in outer sphere hydrogen bonding for Mn is highlighted in cyan and for Fe in orange. For FeSOD, the lysine residues involved in photosynthetic context is shown in pink. The active site residues are marked as I and the dimer residues are represented by .
Structural analysis of available cyanobacterial Fe and MnSODs, confirms that both share a similar active site (i.e., metal ion) being coordinated in the respective isoform by three histidine and an aspartate residue with a ligating solvent molecule (water or OH), a five coordinated trigonal bipyramidal geometry. In Thermosynechococcus elongatus (PDB code 1my6); the Fe ion is coordinated by the carboxylate oxygen (Oδ2) of D161 with the amino group (Nε2) of H79, 27, 165 along with the oxygen atom of the water molecule. The hydrogen bonding distance between Oδ2 (D161) and Nε2 (H27 and H79) is 2.79Å and 3.27Å respectively (Table 1). In case of Anabaena sp (PDB code: 1gv3), the Mn is coordinated by Nε2 of H117, 204, 62 and Oδ2 of D200. The hydrogen bonding between Oδ2 (D200) and Nε2 (H62 and H117) is 2.19Å and 3.33Å respectively. These hydrogen bonds are involved in stabilizing the orientation of the ligand residues in MnSOD [8]. The observed contact surface area (31–35 Å2) between the side chain aspartate oxygen atom (Oδ2) and histidine (Nε2) implies that the metal coordination ligands in the exposed region may perhaps tune the redox potential (Fig 3, 4).
Figure 3
The active site residues of Fe Superoxide dismutase of Thermosynechococcus elonagtus.
Figure 4
The active site residues of Mn Superoxide dismutase of Anabaena sp.
The motif and metal binding sites of Fe and Mn isoforms appear to exhibit similar function. However, the sequence alignment and structural analysis reveal their possible discrimination by three traits to specifically differentiate Fe and Mn isoforms (Table 1 Additional file 1).
Table 1
Discriminatory key to classify indecisive isoforms.
Characteristics
FeSOD
MnSOD
Metal specificity
Fe
Mn
Amino acid length
199–229
200–316
Theoretical molecular weight
21–25 KDa
22–34 KDa
No. of a helix*
13
14
No. of b strand*
3
3
Domains
N & C terminal
N & C terminal
Motif
DVWEHAYY
DVWEHAYY
Active site residues*
Fig 3
Fig 4
Structurally highly conserved metal specific residues
F184XXXA188Q189.......T280......F/Y303
R184XXXG188G189.......G280......W303
Conserved residue with photosynthetic role
K87, K139
None
Transmembrane hydrophobic pocket
Absent
Present
* – Based on the structural analysis of MnSOD of Anabaena sp. (PDB No: 1gv3) and FeSOD of Thermosynechococcus elongatus BP-1 (PDB No: 1my6)
First, is the change in conserved amino acid signature F184X3A188Q189.......T280......F/Y303 in Fe being replaced by R184X3G188G189.......G280......W303 in MnSOD (see Figures 2 and 5).
Figure 5
This figure shows the second quartile of protein sequence alignment of Fe and MnSODs in cyanobacteria. For full image, please see Additional file 1. The conserved aminoacid signature for Fe and MnSODs are highlighted in red and green respectively. Lysine residues of FeSOD involved in photosynthetic context is depicted in pink. The active site residues are labeled as I.
The second notable feature is related to the metal bound solvent molecule that serves as a hydrogen bond to the non-coordinated oxygen of the carbonyl group of the aspartate ligand accepting a hydrogen bond from an outer sphere residue [19]. In MnSOD, it is glutamine Q262 (Fig 2) arising from the end of the β2-strand and H 9 in the C-terminal domain, while in FeSOD, it is tryptophan W243 arising from the middle of the sequence (within the β1) in the C-terminal domain. In the case of cambialistic Fe/MnSOD metalloform reported in archaea (Pyrobaculum aerophilum) [19], the outer-sphere H-bonding residue is histidine. This residue plays a major role in altering the solvent interaction with the active site metal ion in cambialistic Fe/Mn SOD isoform [19]. The sequence analysis of cyanobacterial SODs showed the absence of this histidine residue which probably suggests the absence of cambialistic forms in cyanobacteria. Vance and Miller [20] reported that the most highly conserved residues glutamine Q262 in Mn and Q189 of FeSOD forms the outer sphere hydrogen-bond network exerts a large influence on redox midpoint potential tuning for catalytic activity of SOD's.
The third difference is the presence of two lysine residues, K201 and 255 in FeSOD but not in MnSOD (Fig 2 and 5). These residues seem to be unique and function specific to cyanobacteria among prokaryotes [21]. K201 lines a small pit at the surface of the T. elongatus and of higher plants FeSOD, formed by the loop P202-G203-G204 connecting N and C terminal domains. Likewise, K255 is restricted only to cyanobacteria, indicating its importance in the photosynthetic context [21].
Cyanobacterial MnSOD is the only SOD to be membrane anchored by transmembrane helix [22]. The factor that determines localization of MnSOD is found to span the N terminal which is a hydrophobic transmembrane helix (Fig 1D, 6). The cyanobacterial representatives such as (Synechococcus sp. WH5701 (EAQ76095), Synechococcus sp. RS9917 (EAQ68777), Trichodesmium erythraeum IMS101 (EAO27349), Anabaena variabilis ATCC29413 (ABA21068) and Nostoc sp. PCC7120 (BAB77594)) clearly corroborate this (Fig 6).
Figure 6
This figure shows the upper quartile of protein sequence alignment of Fe and MnSODs in cyanobacteria. For full image, please see Additional file 1. Transmembrane hydrophobic pocket specific for membrane binding in MnSOD at the N-terminal region is highlighted in violet.
Cyanobacterial Cu/ZnSOD isoform bears no resemblance to Fe or Mn or Ni isoform in relation to its primary and tertiary structure. The theoretical molecular weight ranges between 16–23 KDa with an amino acid length of 174–233 residues. Further, study on amino acid composition illustrates that it is rich in Gly (11–16%) forming eight β-sheets (Fig 7A) accredited to be involved in conformation [23] and stability in repeated freeze/thaw cycles and prolonged refrigeration [9]. These isoforms in general have a copper containing domain (Pfam:PF00080) with two different signatures. The first is G-F-H-[ILV]-H-x-[NGT]-[GPDA]-[SQK]-C where the conserved histidine is involved in copper binding, and the second being G-[GA]-G-G-[AEG]-R-[FIL]-[AG]-C-G where C is involved in disulfide bonding (Fig 8). G. violaceus SOD (NP_925116, NP_924927) annotated as 'similar to SOD' contains only copper binding domain and both the signatures are absent. Further confirmation requires additional structural data. Each monomer is comprised of a binuclear metal centre with one Cu and one Zn atom. The noticeable β parallel fold of cyanobacterial Cu/Zn isoform mimics the structure of Salmonella typhimurium Cu/ZnSOD [24] (Fig 7B). The catalytic coordination sphere of Cu2+ ion is by Nδ1 of H103, Nε2 of H105, H147 and H215 and Zn2+ by Nδ1 of three H147, 157, 171 and Oδ1 of one D174 (Fig 8). Besides this, structural comparison designates the two specific hydrogen bonds between the Zn2+ coordinating residues D174-Oδ1... H157-Nδ1 (3.25 Å) and D174-Oδ1... H171-Nε1 (3.18 Å) to ligand stability.
Figure 7
Representative structure ofSalmonella typhimuriumCu/Zn superoxide dismutase. (a) Tetrameric subunits of Cu/ZnSOD. Chain A coded in green, B in pink, C in yellow and D in cyan. (b) Crystallographic structure of functional S. typhimurium Cu/ZnSOD (PDB 1eqw) subunit is represented to highlight the active site residues in ball and stick mode visualized using WebLab ViewerLite 4.2 software.
Figure 8
Sequence alignment of cyanobacterial copper zinc superoxide dismutase with bacterial representatives. Alignment was carried out using Clustal W of BioEdit Package (v.7.0.5) [28]. The active site Cu residues are marked as and Zn in #. The signature 1 residues are highlighted in green and signature 2 in blue.
The fourth canonical form NiSOD is a hexamer (Fig 9A) found only in cyanobacteria [25] and Streptomyces [26, 27] with amino acids ranging from 140–163 and molecular weight between 15–18 KDa. Analysis of available sequences and complete genome sequences revealed that, unicellular Prochlorococcus forms possess only NiSOD, whereas, multicellular filamentous heterocystous and heterotrichous forms lacks this isoform (Table 2). The key for the ubiquity of NiSOD in Prochlorococcus may be due to the primitive photosynthetic machinery and its smallest genome size (between 1669–2434 Kb) by gene rearrangement or loss to maximize the energy economy [28]. The sequence conservation, motif with eleven-residues (HCDGPCVYDPA) in N-terminal region of Ni-hook, along with a nickel containing SOD domain (Pfam:PF09055) forms an unique pattern to identify cyanobacterial NiSOD. Cyanobacterial NiSODs seem to have an assembly of four alpha helices bundle with a short connecting alpha helix, as that of Streptomyces sp. (Fig 9B). The catalytic Ni ion of cyanobacteria is very much analogous to the reported square planar active center with thiolate (C2, based on 1t6u), backbone nitrogen (H1 and C6) ligands and of square pyramidal Ni (II) with an added axial His1 side chain of Streptomyces sp. [29].
Table 2
Annotation of cyanobacterial superoxide dismutases based on sequence and structure conservation.
Organisms
Accession no
Sequence length
Type of SOD in Database
Confirmed isoform from our study
Prochlorococcus marinus AS9601
YP_001009883
157
putative Ni
NiSOD
Prochlorococcus marinus CCMP1986
NP_893411
156
putative Ni
NiSOD
Prochlorococcus marinus CCMP1375
NP_875759
157
Ni
NiSOD
Prochlorococcus marinus MIT 9301
YP_00109170
157
putative Ni
NiSOD
Prochlorococcus marinus MIT 9303
YP_001017980
164
putative Ni
NiSOD
Prochlorococcus marinus MIT 9211
ZP_01004940
140
Ni
NiSOD
Prochlorococcus marinus MIT 9312
YP_397886
157
putative Ni
NiSOD
Prochlorococcus marinus MIT 9313
NP_894173
157
putative Ni
NiSOD
Prochlorococcus marinus MIT 9515
YP_001011769
157
putative Ni
NiSOD
Prochlorococcus marinus NATL1A
YP_0010155334
163
putative Ni
NiSOD
Prochlorococcus marinus NATL2A
YP_292055
163
putative Ni
NiSOD
Synechococcus sp. WH 8102
NP_897719
157
putative Ni
NiSOD
Synechococcus sp. BL107
ZP_01469600
157
putative Ni
NiSOD
ZP_01468043
198
putative SOD
Cu/ZnSOD
Synechococcus sp. CC9605
YP_381196
157
putative Ni
NiSOD
YP_381812
178
SOD precursor (Cu-Zn)
Cu/ZnSOD
Synechococcus sp. CC9311
YP_729969
175
Cu/Zn
Cu/ZnSOD
YP_730975
155
Ni
NiSOD
Synechococcus sp. CC9902
YP_376992
175
putative SOD
Cu/ZnSOD
Crocosphaera watsonii WH 8501
ZP_00517273
159
Hypothetical protein
NiSOD
ZP_00514026
254
SOD
MnSOD
Synechococcus elogatus PCC 6301
YP_171447
229
SOD
FeSOD
1613421A
202
SOD
FeSOD
Synechococcus elogatus PCC 7942
YP_399820
229
SOD
FeSOD
CAB57855
201
SOD
FeSOD
Synechococcus sp. JA-3-3Ab
YP_476221
199
Fe
FeSOD
Synechococcus sp. JA-2-3B'a(2–13)
YP_478710
199
Fe
FeSOD
Synechococcus sp. WH 7805
ZP_01124652
199
SOD
FeSOD
ZP_01123794
174
putative SOD
Cu/ZnSOD
Synechococcus sp. WH 5701
ZP_01084003
199
SOD
FeSOD
ZP_01084015
231
Mn
MnSOD
Synechococcus sp. RS9916
ZP_01470625
199
SOD
FeSOD
ZP_01472508
177
SOD precursor (Cu-Zn)
Cu/ZnSOD
Gloeobacter violaceus PCC 7421
NP_927273
203
SOD
FeSOD
NP_923628
316
SOD
MnSOD
NP_924927
233
similar to SOD
NA*
NP_925116
191
similar to SOD
NA*
Synechococcus sp. RS9917
ZP_01081353
199
SOD
FeSOD
ZP_01080487
229
SOD
MnSOD
Cyanothece sp. CCY0110
ZP_01728505
200
SOD
FeSOD
Thermosyncehococcus elongatus BP-1
NP_682309
200
SOD
FeSOD
NP_680827
240
SOD
MnSOD
Lyngbya sp. PCC8106
ZP_0169885
201
SOD
Cu/ZnSOD
ZP_01619231
201
SOD
FeSOD
Trichodesmium erythraeum IMS101
YP_723986
254
SOD
MnSOD
YP_720765
159
putative Ni
NiSOD
Synechocystis sp. PCC 6803
NP_441347
199
Fe
FeSOD
Spirulina platensis
AAQ22734
170
Fe
FeSOD
Plectonema boryanum UTEX 485
AAA69954
199
Fe
FeSOD
AAA69953
239
superoxide dismutase [Mn] precursor
MnSOD
AAA69950
248
MnSOD
AAA69952
206
MnSOD
Leptolyngbya valderiana BDU20041
AAX84682
144
Mn
MnSOD
Nostoc punctiforme PCC 73102
ZP_00108516
200
SOD
FeSOD
ZP_00112125
249
SOD
MnSOD
ZP_00108372
259
SOD
MnSOD
Nostoc sp. PCC 7120
Q8YSZ1
200
Fe
FeSOD
AAD51417
200
Fe
FeSOD
NP_484114
270
SOD
MnSOD
Anabaena variabilis ATCC 29413
YP_321482
200
Mn/Fe
FeSOD
YP_321963
270
Mn/Fe
MnSOD
Nostoc linckia
AAL25194
200
SOD
FeSOD
Nostoc commune
AAF25009
200
SOD
FeSOD
Nostoc commune CHEN
AAV84021
200
Fe
FeSOD
* Not Assignable (NA)
Figure 9
Schematic view of representative NiSOD subunit and hexameric structure ofStreptomyces coelicolor[PDB 1t6u]. (a) NiSOD biological unit is a hexameric assembly of 4-helix bundles (b) NiSOD subunit with metal binding hook labels at the end of helix-1 along with the metal shaded in yellow is represented by ball and stick mode as visualized in WebLab ViewerLite 4.2 software.
Conclusion
The analysis is based on 64 cyanobacterial SODs available to date in public databases. Among them 2 are described as Fe/Mn, 4 as Cu/Zn and Mn precursor, 16 as putative NiSOD, 11 annotated as Fe, Mn and Cu/Zn isoforms, 29 as possible/putative SOD and 2 as hypothetical proteins.
Thus the present study resolves the incompletely annotated SODs among cyanobacteria (Table 2). Further, 64 cyanobacterial SOD sequences are clearly categorized into 17 NiSOD, 7 Cu/ZnSOD, 24 FeSOD and 14 MnSOD genes, 2 non assignable as they require further structural data. The strict metal specificity, precise sequence and structure among the metalloforms led to discriminate Mn and FeSOD (Table 1). The highly homologous Fe and MnSODs shares a metal binding motif DVWEHAYY without any variation, compared to D-X-[WF]-E-H-[STA]-[FY]-[FY] found in other pro – and eukaryotes.
The whole genome sequences analyses of cyanobacteria reveal that the primitive unicellular Prochlorococcus with simple photosynthetic apparatus possesses only NiSOD. The more evolved middle order forms of cyanobacteria posses a combination of Fe and Ni or Fe and Mn SODs. The most evolved filamentous, heterotrichous and heterocystous forms predominantly have only Fe and Mn metalloforms. However, CuZn also occurs rarely (Table 2).
Methods
The non-redundant database of protein sequences (National center for Biotechnology Information, NIH, Bethesda) were retrieved using the PHI-BLAST [30] search tool using BLOSOM 62 matrix with gap penalities (Existence – 11 and Extension – 1) with a threshold value of 0.005 and optimal limit for cyanobacteria. The query sequence used were Synechococcus sp. JA-3-3Ab with Expasy-PROSITE pattern D-x-[WF]-E-H-[STA]-[FY]2 for Fe/MnSOD; Synechococcus sp. RSS9916 with signature 1 [GA]-[IMFAT]-H-[LIVF]-H-{S}-x-[GP]-[SDG]-x-[STAGDE] and signature 2 (G-[GNHD]-[SGA]-[GR]-x-R-x-[SGAWRV]-C-X(2)-[IV]) for Cu/ZnSOD. In addition, the individual sequences of all the SOD metalloforms were also manually retrieved from public databases (NCBI, KEGG). Identical sequences from the same organism were removed manually. Intoto, 64 sequences representing 24 complete genomes and individual submissions obtained are listed in Table 2 together with the accession numbers and the organisms. Identification of domains associated with SOD proteins were realized using NCBI Conserved Domain Search and Pfam servers
The secondary structure consensus was carried out using nnPREDICT [31] and JPRED [32] for each protein to refine the multiple sequence alignment. Multiple alignments for cyanobacterial Fe and MnSODs; and Cu/ZnSOD sequences were generated using the Clustal W (neighbor-joining) of BioEdit V.7.0.5 [33] program. Default parameter for both the alignments was gap initial penalty- 8 and gap extension penalty of 2. The alignment was fixed under the PAM40 series protein-weight matrices in both the cases. The sequence alignments were displayed graphically using BIOEDIT package [28] with a threshold of 95% consensus residue shading.
Representative crystal structures of available cyanobacterial FeSOD (1my6-Thermosynechococcus elongates BP-1) and MnSOD (1gv3-Anabaena sp. PCC7120) with exception for NiSOD (1t6u-Streptomyces coelicolor) and Cu/ZnSOD (1eqw-Salmonella typhimurium) were retrieved from PDB. The 3D structures were analyzed using SWISS-PDB viewer [34] and graphical representations were done with WebLab viewer lite (V.4.2)
Notes
Declarations
Acknowledgements
This study was supported by Department of Biotechnology, Government of India, New Delhi. The authors also thank Dr. Kaleel Ahmad, Reader, Jamal Mohammed College, Tiruchirappalli, India for his critical comments and valuable suggestions.
Authors’ Affiliations
(1)
National Facility for Marine Cyanobacteria (Sponsored by Department of Biotechnology, Government of India), Bharathidasan University
(2)
School of Physics, Bharathidasan University
References
McCord JM, Fridovich I: Superoxide dismutase. An enzymic function for erythrocuprein (hemocuprein). J Biol Chem. 1969, 244: 6049-6055.PubMedGoogle Scholar
Meier B, Barra D, Bossa F, Calabrese L, Rotilio G: Synthesis of either Fe- or Mn-superoxide dismutase with an apparently identical protein moiety by an anaerobic bacterium dependent on the metal supplied. J Biol Chem. 1982, 257: 13977-13980.PubMedGoogle Scholar
Amano A, Shizukuishi S, Tamagawa H, Iwakura K, Tsunasawa S, Tsunemitsu A: Characterization of superoxide dismutases purified from either anaerobically maintained or aerated Bacteroides gingivalis. J Bacteriol. 1990, 172: 1457-1463.PubMed CentralPubMedGoogle Scholar
Sugio SB, Hiraoka Y, Yamakura F: Crystal structure of cambialistic superoxide dismutase from Porphyromonas gingivalis. Eur J Biochem. 2000, 267: 3487-3495. 10.1046/j.1432-1327.2000.01373.x.PubMedView ArticleGoogle Scholar
Hiraoka BY, Yamakura F, Sugio S, Nakayama K: A change of the metal-specific activity of a cambialistic superoxide dismutase from Porphyromonas gingivalis by a double mutation of Gln-70 to Gly and Ala-142 to Gln. Biochem J. 2000, 345: 345-350. 10.1042/0264-6021:3450345.PubMed CentralPubMedView ArticleGoogle Scholar
Blankenship RE: Molecular evidence for the evolution of photosynthesis. Trends Plant Sci. 2001, 6: 4-6. 10.1016/S1360-1385(00)01831-8.PubMedView ArticleGoogle Scholar
Atzenhofer W, Regelsberger G, Jacob U, Peschek G, Furtmuller P, Huber R, Obinger C: The 2.0A resolution structure of the catalytic portion of a cyanobacterial membrane-bound manganese superoxide dismutase. J Mol Biol. 2002, 321: 479-489. 10.1016/S0022-2836(02)00624-1.PubMedView ArticleGoogle Scholar
Herbert SK, Samson G, Fork DC, Laudenbach DE: Characterization of damage to photosystems I and II in a cyanobacterium lacking detectable iron superoxide dismutase activity. Proc Natl Acad Sci USA. 1992, 89: 8716-8720. 10.1073/pnas.89.18.8716.PubMed CentralPubMedView ArticleGoogle Scholar
Kim JH, Suh KH: Light-dependent expression of superoxide dismutase from cyanobacterium Synechocystis sp. strain PCC 6803. Arch Microbiol. 2005, 183: 218-223. 10.1007/s00203-005-0766-9.PubMedView ArticleGoogle Scholar
Kalib A: Studies on Cyanobacterial tolerance to dessication. Ph.D Dissertation, National Facility for Marine Cyanobacteria, India. 2002Google Scholar
Uma Maheshwari R, Kathirvel E, Anand N: Desiccation-induced Changes in Antioxidant Enzymes, Fatty Acids, and Amino Acids in the Cyanobacterium Tolypothrix scytonemoides. World J Microbiol Biotechnol. 2007, 23: 251-257. 10.1007/s11274-006-9221-6.View ArticleGoogle Scholar
Thomas DJ, Avenson TJ, Thomas JB, Herbert SK: A cyanobacterium lacking iron superoxide dismutase is sensitized to oxidative stress induced with methyl viologen but not sensitized to oxidative stress induced with norflurazon. Plant Physiology. 1998, 116: 1593-1602. 10.1104/pp.116.4.1593.PubMed CentralPubMedView ArticleGoogle Scholar
Saha SK, Uma L, Subramanian G: Nitrogen stress induced changes in the marine cyanobacterium Oscillatoria willei BDU 130511. FEMS Microbiol Ecol. 2003, 45: 263-272. 10.1016/S0168-6496(03)00162-4.View ArticleGoogle Scholar
Wintjens R, Noel C, May AC, Gerbod D, Dufernez F, Capron M, Viscogliosi E, Rooman M: Specificity and phenetic relationships of iron- and manganese-containing superoxide dismutases on the basis of structure and sequence comparisons. J Biol Chem. 2004, 279: 9248-9254. 10.1074/jbc.M312329200.PubMedView ArticleGoogle Scholar
Parker WM, Blake CFC: Iron- and manganese-containing superoxide dismutases can be distinguished by analysis of their primary structures. FEB. 1988, 229: 377-382. 10.1016/0014-5793(88)81160-8.View ArticleGoogle Scholar
Jackson SMJ, Cooper JB: An analysis of structural similarity in the iron and manganese superoxide dismutases based on known structures and sequences. BioMetals. 1998, 11: 159-173. 10.1023/A:1009238214394.PubMedView ArticleGoogle Scholar
Borgstahl GEO, Parge HE, Hickey MJ, Beyer WF, Hallewell RA, Tainer JA: The structure of human mitochondrial manganese superoxide dismutase reveals a novel tetrameric interface of two 4-helix bundles. Cell. 1992, 71: 107-118. 10.1016/0092-8674(92)90270-M.PubMedView ArticleGoogle Scholar
Vance CK, Miller AF: A simple proposal that can explain the inactivity of metal-substituted superoxide dismutases. J Am Chem Soc. 120: 461-467. 10.1021/ja972060j.Google Scholar
Whittaker MM, Whittaker JW: Recombinant superoxide dismutase from a hyperthermophilic archaeon, Pyrobaculum aerophilum. J Biol Inorg Chem. 2000, 5: 402-408.PubMedGoogle Scholar
Regelsberger G, Atzenhofer W, Ruker F, Peschek GA, Jakopitsch C, Paumann Furtmuller PG, Obinger C: Biochemical characterization of a membrane-bound manganese-containing superoxide dismutase from the cyanobacterium Anabaena PCC 7120. J Biol Chem. 2002, 277: 43615-43622. 10.1074/jbc.M207691200.PubMedView ArticleGoogle Scholar
Wolfe F, Schofield O, Falkowski P: The role and evolution of superoxide dismutase in algae. J Phycol. 2005, 2-38.Google Scholar
Pesce A, Battistoni A, Stroppolo ME, Polizio F, Nardini M, Kroll JS, Langford PR, O'Neill P, Sette M, Desideri A, Bolognesi M: Functional and crystallographic characterization of Salmonella typhimurium Cu,Zn superoxide dismutase coded by the sodC virulence gene. J Mol Biol. 2000, 302: 465-478. 10.1006/jmbi.2000.4074.PubMedView ArticleGoogle Scholar
Palenik B, Brahamsha B, Larimer FW, Land M, Hauser L, Chain P, Lamerdin J, Regala W, Allen EE, McCarren J, Paulsen I, Dufresne A, Partensky F, Webb EA, Waterbury J: The genome of a motile marine Synechococcus. Nature. 2003, 424: 1037-1042. 10.1038/nature01943.PubMedView ArticleGoogle Scholar
Youn HD, Kim EJ, Roe JH, Hah YC, Kang SO: A novel nickel-containing superoxide dismutase from Streptomyces spp. Biochem J. 1996, 318: 889-896.PubMed CentralPubMedView ArticleGoogle Scholar
Youn HD, Youn H, Lee JW, Yim YI, Lee JK, Hah YC, Kang SO: Unique isozymes of superoxide dismutase in Streptomyces griseus. Arch Biochem Biophys. 1996, 334: 341-348. 10.1006/abbi.1996.0463.PubMedView ArticleGoogle Scholar
Garcia-Fernandez J, de Marsac N, Diez J: Streamlined regulation and gene loss as adaptive mechanisms in Prochlorococcus for optimized nitrogen utilization in oligotrophic environments. Microbiol Mol Biol Reviews. 2004, 68: 630-638. 10.1128/MMBR.68.4.630-638.2004.View ArticleGoogle Scholar
Cuff JA, Barton GJ: Application of multiple sequence alignment profiles to improve protein secondary structure prediction. Proteins. 2000, 40: 502-511. 10.1002/1097-0134(20000815)40:3<502::AID-PROT170>3.0.CO;2-Q.PubMedView ArticleGoogle Scholar
Hall TA: BioEdit : a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucl Acids Symp Ser. 1999, 41: 95-98.Google Scholar
Jones DT: Protein secondary structure prediction based on position-specific scoring matrices. J Mol Biol. 1999, 292: 195-202. 10.1006/jmbi.1999.3091.PubMedView ArticleGoogle Scholar
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and Zn in #. The signature 1 residues are highlighted in green and signature 2 in blue.
