FIG. 1.

Amino acid sequence alignment for 24 Isf homologs from diverse microorganisms not previously reported (15). The sequence of M. thermophila Isf is included for reference. The sequences included exhibit more than 20% identity with the M. thermophila Isf sequence (191 residues) and bear the conserved cysteine motif. Abbreviations: Ca1, Ca2, and Ca3, ORFs from a C. acetobutylicum unfinished fragment of the complete genome; Cd2, Cd3, and Cd4, ORFs from C. difficile unfinished fragments of the complete genome; Ch1, Ch2, and Ch3, ORFs from Carboxydothermus hydrogenoformans unfinished fragments of the complete genome; De1 and De2, ORFs from two Dehalococcoides ethenogenes unfinished fragments of the complete genome; Dh, ORF from preliminary sequence data for the genome of Desulfitobacterium hafniense (http://www.jgi.doe.gov/JGI_microbial/html/index.html); Dv, ORF from a Desulfovibrio vulgaris unfinished fragment of the complete genome; Eh, ORF from E. histolytica unfinished fragment of the complete genome; Gs, ORF from a Geobacter sulfurreducens unfinished fragment of the complete genome; Mm1 and Mm2, ORFs from preliminary sequence data for the genome of M. mazei provided by the Göttingen Genomic Laboratory (http://www.g21.bio.uni-goettingen.de/); Msb1, Msb2, Msb3, Msb4, and Msb5, ORFs from preliminary sequence data for the genome of Methanosarcina barkeri: Mst, M. thermophila iron-sulfur flavoprotein (GenBank accession no. U50189); and Xf, X. fastidiosa ORF XF1919 (GenBank accession no. AE004011). Residues that are conserved in at least 7 of 10 sequences are shaded. The cysteines in the cysteine motif ligating the 4Fe-4S cluster are indicated by asterisks.