GP46 Redβ mll7977_Ml E EHAP1 EHAP1_Ec GAM Redβ λEXO Redβ _λ RecE EHAP1 STM2633_StLT2 RecE EHAP1 STY2074_Salent orf100a Orf86 Orf40 SbcC RecT SA1794_SaN315 orf43_BPPVL Orf38 Orf86 Orf40 SbcC RecT ORF9 RecT ORF10_BPR1T BMC Genomics 2002, 3 http://www.biomedcentral.com/1471-2164/3/8 XF1648_Xf Ec2360 Redβ λEXO AcylTr Bro UU154_Uu E Redβ PF161_Borhercp ORF245_BPphi31_1 Redβ Orf364 lin1755_Li SbcC Redβ SPy0958_Strpy Redβ Orf364 RecT_BPbIL309 RecT RecE Spy1477_Strpy RecT RecE lin2413_Li λEXO RecT DNAD GP32 Met ORF48_BPA118 λEXO RecT DNAD Met ORF15 gene35_Spp1 YqaK_Bs S RecT_Ec ORFC_Lp λEXO RecT RecE RecT RecE RecT λEXO ORF34.2 ORF34.3 ORF34.4 RecT SSB EndoVII Figure 2 Maximum likelihood tree for the RecT/Redβ superfamily of proteins. The internal branches with RELL bootstrap support >70% are indicated by blue circles. Proteins are designated by their gene names and species abbreviations as in Fig. 1. The gene neighborhoods of the RecT/Redβ superfamily genes are shown in association with the corresponding branches whenever they they contained genes for proteins with plausible functional connections with SSAPs. The hatched boxes repre- sent fragments of ERF (Indicated by E) and SSB (indicated by S) genes encoding C-terminal regions as described in the text. Gene abbreviations are as follows: GP46: GP46 of bacteriophage PSA, GP32:GP32 of bacteriophage PSA, ORF15:ORF15 of Streptococcus thermophilus bacteriophage 7201, ORF40: ORF40 of bacteriophage PVL ORF86:ORF86 of Staphylococcus aureus temperate phage φSLT, Orf100a:0rf100a of Staphylococcus aureus temperate phage φSLT, ORF364: ORF364 of bacteriophage φ31.1, Ec2360: b2360 of E. coli, AcylTr: N-Acyltransferase, Bro: Bro-N domain fused to XF0704, Met: DNA Methyltransferase tococcus and Listeria, and their phages (Fig. 2). E. coli and Legionella pneumophila are the only two γ-proteobacteria that possess this protein, suggesting that they might have acquired RecT via a relatively recent horizontal transfer from Gram-positive bacteria. The sporadic distribution of the RecT and Redβ family proteins in bacterial genomes and their presence in phages suggest that these proteins ultimately are of phage origin and have been co-opted by the bacterial DNA recombination/repair systems. Consist- ent with this, practically all the bacterial members of these families appear to belong to prophages or their remnants, as they are mostly in the neighborhood of what appear to be clearly phage-derived genes. The EHAP1-like family is extremely divergent and represented thus far only in E. coli and the closely related Salmonella. Practically all members of the RecT/Redβ superfamily are single-domain proteins showing extended similarity to each other throughout their globular regions. The only exceptions are the E. coli EHAP1 and the PF161 protein encoded in the Borrelia hermsii circular plasmid, which are fused to C-terminal fragments of the ERF protein (see below). Page 4 of 11 (page number not for citation purposes)