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Structure of the translocation ATPase SecA from Thermotoga maritima
Structural highlights
FunctionSECA_THEMA 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). 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 forms a functional complex with the protein-conducting SecY channel to translocate polypeptides across the bacterial cell membrane. SecA recognizes the translocation substrate and catalyzes its unidirectional movement through the SecY channel. The recent crystal structure of the Thermotoga maritima SecA-SecYEG complex shows the ATPase in a conformation where the nucleotide-binding domains (NBDs) have closed around a bound ADP-BeFx complex and SecA's polypeptide-binding clamp is shut. Here, we present the crystal structure of T. maritima SecA in isolation, determined in its ADP-bound form at 3.1 A resolution. SecA alone has a drastically different conformation in which the nucleotide-binding pocket between NBD1 and NBD2 is open and the preprotein cross-linking domain has rotated away from both NBDs, thereby opening the polypeptide-binding clamp. To investigate how this clamp binds polypeptide substrates, we also determined a structure of Bacillus subtilis SecA in complex with a peptide at 2.5 A resolution. This structure shows that the peptide augments the highly conserved beta-sheet at the back of the clamp. Taken together, these structures suggest a mechanism by which ATP hydrolysis can lead to polypeptide translocation. Conformational flexibility and peptide interaction of the translocation ATPase SecA.,Zimmer J, Rapoport TA J Mol Biol. 2009 Dec 11;394(4):606-12. Epub 2009 Oct 20. PMID:19850053[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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