3on0
From Proteopedia
Crystal structure of the pED208 TraM-sbmA complex
Structural highlights
FunctionTRAM8_ECOLX Conjugative DNA transfer (CDT) is the unidirectional transfer of ssDNA plasmid from a donor to a recipient cell. It is the central mechanism by which antibiotic resistance and virulence factors are propagated in bacterial populations. Part of the relaxosome, which facilitates a site- and strand-specific cut in the origin of transfer by TraI, at the nic site (By similarity). TraM binds to three principal regions in the oriT (transfer origin) region; 2 are required for autoregulation while the other is required for plasmid transfer. Plasmid specificity is conferred by the TraD-TraM pair. Publication Abstract from PubMedThe conjugative transfer of F-like plasmids such as F, R1, R100 and pED208, between bacterial cells requires TraM, a plasmid-encoded DNA-binding protein. TraM tetramers bridge the origin of transfer (oriT) to a key component of the conjugative pore, the coupling protein TraD. Here we show that TraM recognizes a high-affinity DNA-binding site, sbmA, as a cooperative dimer of tetramers. The crystal structure of the TraM-sbmA complex from the plasmid pED208 shows that binding cooperativity is mediated by DNA kinking and unwinding, without any direct contact between tetramers. Sequence-specific DNA recognition is carried out by TraM's N-terminal ribbon-helix-helix (RHH) domains, which bind DNA in a staggered arrangement. We demonstrate that both DNA-binding specificity, as well as selective interactions between TraM and the C-terminal tail of its cognate TraD mediate conjugation specificity within the F-like family of plasmids. The ability of TraM to cooperatively bind DNA without interaction between tetramers leaves the C-terminal TraM tetramerization domains free to make multiple interactions with TraD, driving recruitment of the plasmid to the conjugative pore. Structural basis of cooperative DNA recognition by the plasmid conjugation factor, TraM.,Wong JJ, Lu J, Edwards RA, Frost LS, Glover JN Nucleic Acids Res. 2011 May 11. PMID:21565799[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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