Complex behavior in solution of homodimeric SecA
TLDR
Analytical centrifugation, as well as column chromatography coupled with multiangle light scatter, is used to show that in solution SecA undergoes at least two monomer‐dimer equilibrium reactions that are sensitive to temperature and to concentration of salt.Abstract:
SecA, a homodimeric protein involved in protein export in Escherichia coli, exists in the cell both associated with the membrane translocation apparatus and free in the cytosol. SecA is a multifunctional protein involved in protein localization and regulation of its own expression. To carry out these functions, SecA interacts with a variety of proteins, phospholipids, nucleotides, and nucleic acid and shows two enzymic activities. It is an ATPase and a helicase. Its role during protein localization involves interaction with the precursor polypeptides to be exported, the cytosolic chaperone SecB, and the SecY subunit of the membrane-associated translocase, as well as with acidic phospholipids. At the membrane, SecA undergoes a cycle of binding and hydrolysis of ATP coupled to conformational changes that result in translocation of precursors through the cytoplasmic membrane. The helicase activity of SecA and its affinity for its mRNA are involved in regulation of its own expression. SecA has been reported to exist in at least two conformational states during its functional cycle. Here we have used analytical centrifugation, as well as column chromatography coupled with multiangle light scatter, to show that in solution SecA undergoes at least two monomer-dimer equilibrium reactions that are sensitive to temperature and to concentration of salt.read more
Citations
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Journal ArticleDOI
Protein translocation across the bacterial cytoplasmic membrane.
TL;DR: This review summarizes the present knowledge of the mechanism and structure of the Sec translocase, with a special emphasis on unresolved questions and topics of current research.
Journal ArticleDOI
Protein translocation by the Sec61/SecY channel.
TL;DR: In this article, three different mechanisms, each requiring a different set of channel binding partners, are employed to move polypeptide substrates: the ribosome feeds the polyPEptide chain directly into the channel, a ratcheting mechanism is used by the eukaryotic endoplasmic reticulum chaperone BiP, and a pushing mechanism is utilized by the bacterial ATPase SecA.
Protein translocation by the Sec61/SecY channel
TL;DR: Structural studies illustrate how the protein-conducting channel translocates proteins across cellular membranes and integrates proteins containing hydrophobic transmembrane segments into lipid bilayers.
Journal ArticleDOI
Mechanisms of Sec61/SecY-Mediated Protein Translocation Across Membranes
Eunyong Park,Tom A. Rapoport +1 more
TL;DR: Structural and biochemical data show how the channel opens during translocation, translocates soluble proteins, releases hydrophobic segments of membrane proteins into the lipid phase, and maintains the barrier for small molecules.
Journal ArticleDOI
Protein secretion systems and adhesins: The molecular armory of Gram-negative pathogens
Roman G. Gerlach,Michael Hensel +1 more
TL;DR: An overview on the recent understanding of the assembly of fimbrial and non-fimbrial adhesins and the role of type I, III and V secretion systems and specialized branches of the general secretion pathway in their biogenesis is given.
References
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