2ibm
A novel dimer interface and conformational changes revealed by an X-ray structure of B. subtilis SecA
Structural highlights
FunctionSECA_BACSU Part of the Sec protein translocase complex. Interacts with the SecYEG preprotein conducting channel. Has a central role in coupling the hydrolysis of ATP to the transfer of proteins into and across the cell membrane, serving as an ATP-driven molecular motor driving the stepwise translocation of polypeptide chains across the membrane (By similarity).[HAMAP-Rule:MF_01382] 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 PubMedThe SecA ATPase moves polypeptides post-translationally across the plasma membrane of eubacteria, but the mechanism of transport is still unclear. We describe the crystal structure of a novel dimeric form of Bacillus subtilis SecA. Dimerization of SecA occurs at the prominent groove formed by the nucleotide binding domain 2 (nbd2) and the preprotein cross-linking (ppx) domain. The dimer interface is very large, burying approximately 5400 A(2) of solvent accessible surface per monomer. Single cysteine disulfide cross-linking shows the presence of this novel SecA dimer in solution. In addition, other dimers also exist in solution, arguing that they all are in equilibrium with monomeric SecA and supporting the idea that the monomer may be the functional species. Dimerization of SecA causes an alpha-helix of one subunit to convert to a short beta-strand that participates in beta-sheet formation with strands in the other subunit. This conversion of secondary structure elements occurs close to the connection between the nbd1 and ppx domains, a potential site of interaction with translocation substrate. Comparing the different X-ray structures of B. subtilis SecA suggests that small changes in the nucleotide binding domains could be amplified via helix 1 of the helical scaffold domain (hsd) to generate larger movements of the domains involved in polypeptide binding. A novel dimer interface and conformational changes revealed by an X-ray structure of B. subtilis SecA.,Zimmer J, Li W, Rapoport TA J Mol Biol. 2006 Dec 1;364(3):259-65. Epub 2006 Aug 22. PMID:16989859[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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