TraM mediates signalling between transferosome and relaxosome
TraM is a plasmid encoded DNA-binding protein that is essential for conjugative transfer of F-like plasmids (e.g. F, R1, R100 and pED208) between bacterial cells. Bacterial conjugation, a form of horizontal gene transfer between cells, is an important contributor to bacterial genetic diversity, enabling virulence and antibiotics resistance factors to rapidly spread in medically important human pathogens. Mutation studies have shown that TraM is required for normal levels of transfer gene expression as well as for efficient site-specific single-stranded DNA cleavage at the origin of transfer (oriT). TraM tetramers bridge oriT to a key component of the conjugative pore, the coupling protein TraD. The N-terminal ribbon-helix-helix (RHH) domain of TraM is able to cooperatively bind DNA in a staggered arrangement without interaction between tetramers. This allows the C-terminal TraM tetramerization domains to be free to make multiple interactions with TraD, thus driving plasmid recruitment to the conjugative pore.
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