Domain architectures and conserved gene neighborhoods of the SLBB superfamily. (A) Representative architectures are grouped according to family/clade type and labeled by gene name, organism abbreviation, and gi number; demarcated by underscores. Individual domains in architectures are depicted as colored polygons. (B) A sampling of conserved gene neighborhoods found in association with the SLBB domain, with genes depicted as boxed arrows. The SLBB members of the depicted gene neighborhoods are labeled below by gene name, organism abbreviation, and gi number; demarcated by underscores. The family/clade name of the SLBB domain is given to the left in each architecture. Names are given at the top of genes in neighborhoods, where appropriate. The large PduS operon is broken into commonly-observed gene clusters; each boxed arrow enclosed by a dotted line represents such a cluster. ComEA proteins are always in the vicinity of the two-domain ComEC protein that has an integral membrane domain predicted to form a pore through which the DNA is transported into the cell and a metallo-β-lactamase-like domain that may serve as a DNA nuclease during the uptake DNA from the outer cell wall. Additional organism abbreviations not given in Figure 1: Mhun, Methanospirillum hungatei; Mmaz, Methanosarcina mazei; Dred, Desulfotomaculum reducens; Swol, Syntrophomonas wolfei; Valg, Vibrio alginolyticus; Rleg, Rhizobium leguminosarum; and Msp, Mycobacterium sp. MCS. Additional abbreviations: SO, Sulfite Oxidoreductase; β-P, β-propeller; Fer4, 4Fe-S ferrodoxin; HTH, Helix-Turn-Helix; HhH, Helix-hairpin-Helix; RFCδ, RFC clamp loader subunit; LMW, low-molecular weight; and O-Ag, O-antigen.