Comparative analysis of the N-terminal sequence of Geobacter sulfurreducens AM-1 methacrylate reductase

Comparative analyses of the amino acid sequence of the N-terminus of methacrylate reductase (50 kDa) from the anaerobic bacterium Geobacter sulfurreducens AM-1 revealed significant similarity to the sites of flavocytochromes c and flavin-containing proteins of anaerobic bacteria from the genera Anaero-myxobacter, Campylobacter, Desulfatibacillum, Desulfuromonas, Geobacter, Parasutterella, Shewanella, Sulfurospirillum, Sutterella, and Wolinella (belonging to four classes of the Proteobacteria), Denitrovibrio of the phylum Deferribacteres, Desulfitobacterium of the phylum Firmicutes, Eggerthella and Slackia of the phylum Actinobacteria, and Spirochaeta of the phylum Spirochaetes. High homology was also revealed between the methacrylate reductase amino acid sequence and the flavoproteins of aerobic bacteria Frankia and Gordonia from the phylum Actinobacteria and of the archaeon Haloterrigena turkmenica from the phylum Euryarchaeota. Among 11 Geobacter strains with known genomes, only G. lovleyi SZ capable of chlororespiration was found to contain an amino acid fragment of flavocytochrome c with pronounced similarity (80%) to the N-terminus of methacrylate reductase. The physiological properties common to these bacteria are discussed. Molecular masses and the hypothetical functions and localization of the homologous proteins are analyzed. The grouping of proteins according to the phylogenetic affiliation of their owners is discussed. Hypotheses concerning the distribution and evolutionary role of such proteins in microorganisms are suggested.