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Lu, J, Wong, JJ, Edwards, RA, Manchak, J, Frost, LS and Glover, JN (2008) Structural basis of specific TraD-TraM recognition during F plasmid-mediated bacterial conjugation. Mol. Microbiol. 70:89-99


F plasmid-mediated bacterial conjugation requires interactions between a relaxosome component, TraM, and the coupling protein TraD, a hexameric ring ATPase that forms the cytoplasmic face of the conjugative pore. Here we present the crystal structure of the C-terminal tail of TraD bound to the TraM tetramerization domain, the first structural evidence of relaxosome-coupling protein interactions. The structure reveals the TraD C-terminal peptide bound to each of four symmetry-related grooves on the surface of the TraM tetramer. Extensive protein-protein interactions were observed between the two proteins. Mutational analysis indicates that these interactions are specific and required for efficient F conjugation in vivo. Our results suggest that specific interactions between the C-terminal tail of TraD and the TraM tetramerization domain might lead to more generalized interactions that stabilize the relaxosome-coupling protein complex in preparation for conjugative DNA transfer.


PubMed Online version:10.1111/j.1365-2958.2008.06391.x


Amino Acid Sequence; Bacterial Proteins/genetics; Conjugation, Genetic; DNA, Bacterial/genetics; Escherichia coli/genetics; Escherichia coli Proteins/genetics; F Factor/genetics; Membrane Proteins/genetics; Molecular Sequence Data; Mutagenesis, Site-Directed; Promoter Regions, Genetic; Protein Interaction Domains and Motifs; Sequence Alignment



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0009291: unidirectional conjugation



Table 2:

To understand the importance of the C-terminal tail of TraD for conjugation, we tested the ability of TraD mutants to complement conjugation of a plasmid derived from F, pOX38-D411, in which traD is knocked out (Table 2). Deletion of the C-terminal 141 amino acids of TraD (TraD576*) resulted in a 104-fold decrease in conjugation efficiency, compared with wild-type TraD, consistent with previous results (Sastre et al., 1998). This deletion removes the entire C-terminal tail but leaves intact the ATPase domain. Deletion of just the C-terminal eight amino acids (TraD709*) resulted in a 103-fold decrease in conjugation compared with the wild-type control, indicating that this region is critical for the normal function of the C-terminal tail in initiating contact with TraM.


CACAO 12510


See also


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