FIG. 1.

Determination of functional regions of TcpH. (A) Diagrammatic presentation of deletions and site-directed substitutions of TcpH. The predicted domains in wild-type TcpH (832 aa) are presented at the top of the diagram. Black boxes represent putative TMDs, and checked boxes represent predicted coiled-coil domains. The numbers represent amino acid sequence positions. All of the plasmids express TcpH proteins with C-terminal truncations, with the exception of pJIR3115, which is the second to last TcpH derivative represented. In pJIR3115, an internal sequence (encoding aa 311 to 450) of tcpH was deleted. Three independent plasmids expressed the following TcpH site-directed substitutions: pJIR3135 (S1; ₂₄₂VQAAA₂₄₆), pJIR3145 (S2; ₂₈₇DAAAK₂₉₁), and pJIR3134 (S3; ₅₄₅AAA₅₄₇). (B) Conjugation frequencies of complemented tcpH mutants. Plasmids expressing the various TcpH derivatives (as indicated below the graph) were used to transform the transfer-deficient tcpH mutant JIR4885, and the resultant transformants were used independently as donors in matings with strain JIR4394 as the recipient. The frequency of conjugative transfer is reported as the number of transconjugants per donor cell. No transfer was observed with the TcpH_1-128, TcpH_1-291, or TcpH_1-475 derivative (data not shown).