SecA

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==Introduction==
==Introduction==
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The [http://www.rcsb.org/pdb/explore/explore.do?structureId=3JV2 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.
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The [http://www.nature.com/nature/journal/v455/n7215/full/nature07335.html SecA] The ATPase SecA drives the post-translational translocation of proteins through the SecY channel in the bacterial inner membrane. SecA is a dimer that can dissociate into monomers under certain conditions. Many bacterial proteins are transported post-translationally across the inner membrane by the Sec machinery, which consists of two essential components (1-4). One is the SecY complex, which forms a conserved heterotrimeric protein-conducting channel in the inner membrane (5, 6). The other is SecA, a cytoplasmic ATPase, which "pushes" substrate polypeptide chains through the SecY channel (7).
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{{ STRUCTURE_3jv2 | PDB=3jv2 | SCENE=Sandbox_158/Scene_1/1 }}
{{ STRUCTURE_3jv2 | PDB=3jv2 | SCENE=Sandbox_158/Scene_1/1 }}
==Reaction==
==Reaction==

Revision as of 20:26, 23 March 2010

Introduction

The SecA The ATPase SecA drives the post-translational translocation of proteins through the SecY channel in the bacterial inner membrane. SecA is a dimer that can dissociate into monomers under certain conditions. Many bacterial proteins are transported post-translationally across the inner membrane by the Sec machinery, which consists of two essential components (1-4). One is the SecY complex, which forms a conserved heterotrimeric protein-conducting channel in the inner membrane (5, 6). The other is SecA, a cytoplasmic ATPase, which "pushes" substrate polypeptide chains through the SecY channel (7).




Template:STRUCTURE 3jv2

Reaction

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