2ibm
From Proteopedia
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A novel dimer interface and conformational changes revealed by an X-ray structure of B. subtilis SecA
Overview
The 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.
About this Structure
2IBM is a Single protein structure of sequence from Bacillus subtilis with ADP as ligand. Full crystallographic information is available from OCA.
Reference
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
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