The bacterial ATPase SecA functions as a monomer in protein translocation

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...

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Bibliographic Details
Published in:The Journal of biological chemistry Vol. 280; no. 10; p. 9097
Main Authors: Or, Eran, Boyd, Dana, Gon, Stéphanie, Beckwith, Jonathan, Rapoport, Tom
Format: Journal Article
Language:English
Published: United States 11.03.2005
Subjects:
Adenosine Triphosphatases - chemistry
Adenosine Triphosphatases - genetics
Adenosine Triphosphatases - metabolism
Amino Acid Sequence
Bacillus subtilis - enzymology
Bacillus subtilis - growth & development
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Escherichia coli - enzymology
Kinetics
Membrane Transport Proteins - chemistry
Membrane Transport Proteins - genetics
Membrane Transport Proteins - metabolism
Models, Molecular
Plasmids - genetics
Protein Structure, Secondary
Protein Subunits - chemistry
Proteolipids - metabolism
Recombinant Proteins - chemistry
Recombinant Proteins - metabolism
SEC Translocation Channels
SecA Proteins
Sequence Deletion
ISSN:0021-9258
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Summary: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.
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ISSN:0021-9258
DOI:10.1074/jbc.M413947200