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Escherichia coli SecB Protein Associates with Exported Protein Precursors in vivo
Carol A. Kumamoto
Proceedings of the National Academy of Sciences of the United States of America
Vol. 86, No. 14 (Jul. 15, 1989), pp. 5320-5324
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/34471
Page Count: 5
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The product of the Escherichia coli secB gene is required for efficient export of proteins across the cytoplasmic membrane. The studies described in this report show that in wild-type growing cells, SecB protein associates with precursor forms of exported proteins, such as the periplasmic maltose-binding protein (MBP) and the outer-membrane proteins LamB and OmpA. In contrast, the cytoplasmic protein β -galactosidase was not found in association with SecB. Pulse--chase analysis showed that the SecB--precursor MBP complex was short lived, as expected for a complex that represents an intermediate in the protein-export pathway. The results support the hypothesis that SecB protein associates with exported protein precursors in the cytoplasm and dissociates prior to or during translocation of precursors across the cell membrane.
Proceedings of the National Academy of Sciences of the United States of America © 1989 National Academy of Sciences