The biosynthetic machinery for [Fe-S] cluster formation in Gram-positive bacteria. (A) Comparison of the genetic organization of genes involved in the [Fe-S] cluster assembly. Genes having homologous sequences or similar functions between the two systems are color-coded: E. coli ISC and SUF machineries and conserved ORFs coding for putative SUF machinery in Gram-positive bacteria. (B) Neighbour-Joining phylogenetic analysis of protein sequences. (C) Comparison of sequences from members of the NifU/IscU/SufU orthologues. Cysteines are presented as yellow, aspartate as green, LPPVK of IscU in red, and the characteristic Gram-positive insertion in blue.