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Table 2 High conservation of residues facing the channel interior in all FNT channelsa

From: Anion-selective Formate/nitrite transporters: taxonomic distribution, phylogenetic analysis and subfamily-specific conservation pattern in prokaryotes

Residueb

Residues in the positionc

Conservation (%)d

Remarkse

I45 (TM1)

I(55), V, M, L

96.7

Hydrophobic

F75 (TM2a)

F(79), Y

98.8

Part of the central constriction

C82 (TM2a)

V(52), I, L

93.0

Hydrophobic

V83 (TM2a)

V(39), I(33), L, M

86.7

Hydrophobic

D88 (Ω-loop)

E(58), D

80.7

Acidic

L89 (Ω-loop)

L(99)

99.9

Part of cytoplasmic slit (closed)

T91 (Ω-loop)

T(98)

97.9

Part of cytoplasmic slit (closed)

S92 (Ω-loop)

G(50), S, A

79.1

End of Ω-loop; small and weakly polar

N121 (TM3)

N(99)

99.4

Hydrophilic, invariant

A171 (TM4)

C(62), S, A, G

99.9

Close to S-loop; small and weakly polar

N172 (TM4)

N(78)

78.4

Part of cytoplasmic slit (open)

V175 (TM4)

V(81), I, M

99.9

Part of cytoplasmic slit (closed)

V179 (TM4)

V(64), I, L, M

86.2

Hydrophobic

K191 (TM5a)

K(83), R, E

96.4

Basic

M195 (TM5a)

I(43), M, V, L

88.2

Hydrophobic

V199 (TM5a)

I(39), L, V

76.9

Hydrophobic

F202 (TM5)

F(78)

78.5

Part of central constriction ring

G206 (S-loop)

G(74), S, T

79.0

Small and weakly polar

H209 (S-loop)

H(99)

98.7

Part of central constriction ring

N213 (TM5b)

N(76)

76.5

Hydrophilic

N262 (TM6)

N(100)

100.0

Hydrophilic, invariant

  1. aAll 2206 FNT channels from bacteria, archaea and eukaryotes were considered for this analysis
  2. bResidue numbers correspond to that of formate channel structure as available in the PDB ID: 3KCU. Occurrence of these residues in the transmembrane segsments or the functionally important loop regions is also indicated. Residues forming the two constriction regions are shown in bold and italic
  3. cPercentage conservation of the most frequently observed residue(s) is indicated in brackets
  4. dPercentage conservation as observed in all 2206 FNT channels
  5. eChemical nature or the location with respect to the channel interior of the conserved residue is mentioned