Fig. 2

Molecular modeling, structural comparison and amino acid sequence conservation of the proteins encoded by ssu1 and ssu2 predicted operons. Structural comparisons are shown for (a) X. citri SsuA1 (Xac0849) and the alkanesulfonate-binding protein SsuA2 [2]; (b) SsuD1 (Xac0850) with the crystal structure of the E. coli monooxygenase SsuD [8]; and (c) SlfA (Xac0851) with the crystal structure of the E. coli alkanesulfonate FMN reductase SsuE [7]. Protein structures are shown in gray cartoon and the putative residues involved in the substrate binding in magenta stick. Amino acid sequence alignment of the pocket regions are shown below the structures including the related proteins for each group with residues of the active site shown in bold. Amino acid sequence identity of the periplasmic-binding proteins, monooxygenases and oxidoreductases are respectively compared in the tables (d), (e) and (f). All the proteins used for sequence analysis, structural comparison and molecular modeling are described in Additional file 1: Table A1 and Additional file 4: Table A4 from Additional files. Sequence alignments were performed with ClustalX [34]