The structural view of bacterial translocation-specific chaperone SecB: implications for function
Article first published online: 9 SEP 2005
Volume 58, Issue 2, pages 349–357, October 2005
How to Cite
Zhou, J. and Xu, Z. (2005), The structural view of bacterial translocation-specific chaperone SecB: implications for function. Molecular Microbiology, 58: 349–357. doi: 10.1111/j.1365-2958.2005.04842.x
- Issue published online: 19 SEP 2005
- Article first published online: 9 SEP 2005
- Accepted 5 August, 2005.
SecB is a molecular chaperone that functions in bacterial post-translational protein translocation pathway. It maintains newly synthesized precursor polypeptide chains in a translocation-competent state and guides them to the translocon via its high-affinity binding to the ligand as well as to the membrane-embedded ATPase SecA. Recent advances in elucidating the structures of SecB have enabled the examination of protein function in the structural context. Structures of SecB from both Haemophilus influenzae and Escherichia coli support the early two-subsite polypeptide-binding model. In addition, the detailed molecular interaction between SecB and SecA was revealed by a structure of SecB in complex with the C-terminal zinc-containing domain of SecA. These observations explain the dual role of SecB plays in the translocation pathway, as a molecular chaperone and a specific targeting factor. A model of SecB–SecA complex suggests that the binding of SecA to SecB changes the conformation of the polypeptide binding sites in the chaperone, enabling transfer of precursor polypeptides from SecB to SecA. Recent studies also show the presence of a second zinc-independent SecB binding site in SecA and the new interaction might contribute to the function of SecB.