Amino acid sequence of MobC protein from RA3 (IncU). A. Ribbon-helix-helix (RHH) motifs of the plasmid proteins involved in conjugative transfer or stable maintenance: TraY of F [Uniprot:P06627]; ParG of TP228 [Uniprot: Q70W75], CopG of Streptococcus plasmid pLS1 [Uniprot:P13920], TrwA of R388 [Uniprot: Q04229], Omega of pSM19035 [Uniprot: Q83UM6], MbeC of ColE1 [Uniprot: P13657] and NikA of R64 [Uniprot: Q79VV8]. The numbers in brackets correspond to the first amino acid residue of RHH motif. Similar residues in seven to nine representatives are shadowed in white on black, those similar in four to six representatives are shadowed grey. B. MobC family of putative conjugative auxiliary proteins from the IncU plasmids (due to the high similarity only MobC of RA3 is shown as the representative of IncU group) [GenBank: ABD64841] and PromA groups (Orf15 of pSB102 [GenBank: NP_361029], MobC of pTer331 [GenBank: YP_001672038] and MobC of pMRAD02 [GenBank: ACB28263]. Putative RHH motif and a highly conserved “mobilization protein motif” are shown. Similar residues in three or four representatives are shadowed in white on black, those similar in two are shadowed grey. Black arrows mark the C-termini of truncated MobCs analyzed in this work.