2g7o
From Proteopedia
Protonation-mediated structural flexibility in the F conjugation regulatory protein, TraM
Structural highlights
Function[TRAM1_ECOLI] 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. Cooperatively binds 3 regions in the F plasmid oriT locus; 2 are required for autoregulation while the other is required for plasmid transfer. Bends oriT DNA less than 50 degrees. Plasmid specificity is conferred by the TraD-TraM pair.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedTraM is essential for F plasmid-mediated bacterial conjugation, where it binds to the plasmid DNA near the origin of transfer, and recognizes a component of the transmembrane DNA transfer complex, TraD. Here we report the 1.40 A crystal structure of the TraM core tetramer (TraM58-127). TraM58-127 is a compact eight-helical bundle, in which the N-terminal helices from each protomer interact to form a central, parallel four-stranded coiled-coil, whereas each C-terminal helix packs in an antiparallel arrangement around the outside of the structure. Four protonated glutamic acid residues (Glu88) are packed in a hydrogen-bonded arrangement within the central four-helix bundle. Mutational and biophysical analyses indicate that this protonated state is in equilibrium with a deprotonated tetrameric form characterized by a lower helical content at physiological pH and temperature. Comparison of TraM to its Glu88 mutants predicted to stabilize the helical structure suggests that the protonated state is the active form for binding TraD in conjugation. Protonation-mediated structural flexibility in the F conjugation regulatory protein, TraM.,Lu J, Edwards RA, Wong JJ, Manchak J, Scott PG, Frost LS, Glover JN EMBO J. 2006 Jun 21;25(12):2930-9. Epub 2006 May 18. PMID:16710295[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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