A mutation of Escherichia coli SecA protein that partially compensates for the absence of SecB.
The Escherichia coli SecB protein is a cytosolic chaperone protein that is required for rapid export of a subset of exported proteins. To aid in elucidation of the activities of SecB that contribute to rapid export kinetics, mutations that partially suppressed the export defect caused by the absence of SecB were selected. One of these mutations improves protein export in the absence of SecB and is the result of a duplication of SecA coding sequences, leading to the synthesis of a large, in-frame fusion protein. Unexpectedly, this mutation conferred a second phenotype. The secA mutation exacerbated the defective protein export caused by point mutations in the signal sequence of pre-maltose-binding protein. One explanation for these results is that the mutant SecA protein has sustained a duplication of its binding site(s) for exported protein precursors so that the mutant SecA is altered in its interaction with precursor molecules.
McFarland
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Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Francetić
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O
Kumamoto
C A
CA
D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D002874:Chromosome Mapping; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype; D011498:Protein Precursors / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D011498:Protein Precursors; D000069816:SEC Translocation Channels; C057842:SecB protein, Bacteria; C461599:maltose transport system, E coli; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins