3bxz | pdb_00003bxz
Crystal structure of the isolated DEAD motor domains from Escherichia coli SecA
Structural highlights
Function[SECA_ECOLI] Required for protein export, interacts with the SecYEG preprotein conducting channel. SecA has a central role in coupling the hydrolysis of ATP to the transfer of proteins into and across the cell membrane, serving both as a receptor for the preprotein-SecB complex and as an ATP-driven molecular motor driving the stepwise translocation of polypeptide chains across the membrane.[1] 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 preprotein cross-linking domain and C-terminal domains of Escherichia coli SecA were removed to create a minimal DEAD motor, SecA-DM. SecA-DM hydrolyzes ATP and has the same affinity for ADP as full-length SecA. The crystal structure of SecA-DM in complex with ADP was solved and shows the DEAD motor in a closed conformation. Comparison with the structure of the E. coli DEAD motor in an open conformation (Protein Data Bank ID 2FSI) indicates main-chain conformational changes in two critical sequences corresponding to Motif III and Motif V of the DEAD helicase family. The structures that the Motif III and Motif V sequences adopt in the DEAD motor open conformation are incompatible with the closed conformation. Therefore, when the DEAD motor makes the transition from open to closed, Motif III and Motif V are forced to change their conformations, which likely functions to regulate passage through the transition state for ATP hydrolysis. The transition state for ATP hydrolysis for the SecA DEAD motor was modeled based on the conformation of the Vasa helicase in complex with adenylyl imidodiphosphate and RNA (Protein Data Bank ID 2DB3). A mechanism for chemical-mechanical coupling emerges, where passage through the transition state for ATP hydrolysis is hindered by the conformational changes required in Motif III and Motif V, and may be promoted by binding interactions with the preprotein substrate and/or other translocase domains and subunits. Analysis of the isolated SecA DEAD motor suggests a mechanism for chemical-mechanical coupling.,Nithianantham S, Shilton BH J Mol Biol. 2008 Nov 7;383(2):380-9. Epub 2008 Aug 22. PMID:18761349[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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