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Cell. 1988 Apr 22;53(2):273-83.

The antifolding activity of SecB promotes the export of the E. coli maltose-binding protein.

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Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27514.


Evidence is presented that the E. coli secB gene encodes a soluble protein that interacts with the mature region of the precursor maltose-binding protein (MBP), and promotes MBP export by preventing premature folding of the newly synthesized polypeptide into an export-incompetent form. The interaction of SecB with MBP was indicated by the finding that synthesis of various export-defective MBP species interfered with normal protein export by limiting SecB availability. The antifolding activity of SecB was demonstrated by the following: the defect in MBP export in SecB- cells was suppressed by mutational alterations affecting MBP folding; export of a mutant MBP that is accomplished in a strictly posttranslational mode was totally blocked in SecB- cells; and the rate of folding of wild-type MBP synthesized in vitro was found to be accelerated when SecB was absent and greatly retarded when excess SecB was present.

[Indexed for MEDLINE]

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