Abstract
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. To address the functional importance of the monomeric state, we generated an Escherichia coli SecA mutant that is almost completely monomeric (>99%), consistent with predictions from the crystal structure of Bacillus subtilis SecA. In vitro, the monomeric derivative retained significant activity in various assays, and in vivo, it sustained 85% of the growth rate of wild type cells and reduced the accumulation of precursor proteins in the cytoplasm. Disulfide cross-linking in intact cells showed that mutant SecA is monomeric and that even its parental dimeric form is dissociated. Our results suggest that SecA functions as a monomer during protein translocation in vivo.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases / chemistry*
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism*
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Amino Acid Sequence
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Bacillus subtilis / enzymology
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Bacillus subtilis / growth & development
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Escherichia coli / enzymology
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Kinetics
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Membrane Transport Proteins / chemistry*
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Membrane Transport Proteins / genetics
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Membrane Transport Proteins / metabolism*
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Models, Molecular
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Plasmids / genetics
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Protein Structure, Secondary
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Protein Subunits / chemistry
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Proteolipids / metabolism
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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SEC Translocation Channels
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SecA Proteins
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Sequence Deletion
Substances
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Bacterial Proteins
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Membrane Transport Proteins
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Protein Subunits
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Proteolipids
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Recombinant Proteins
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SEC Translocation Channels
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proteoliposomes
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Adenosine Triphosphatases
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SecA Proteins