SecA-dependent quality control of intracellular protein localization
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Edited by H. Ronald Kaback, University of California, Los Angeles, CA (received for review July 16, 2003)
Abstract
Complex secretion machineries mediate protein translocation across cellular membranes. These machines typically recognize their substrates via signal sequences, which are required for proper targeting to the translocon. We report that during posttranslational secretion the widely conserved targeting factor SecA performs a quality-control function that is based on a general chaperone activity. This quality-control mechanism involves assisted folding of signal sequenceless proteins, thereby excluding them from the secretion process. These results suggest that SecA channels proteins into one of two key pathways, posttranslational secretion or folding in the cytoplasm. Implications of this finding for intracellular protein localization are discussed.
Footnotes
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↵ * To whom correspondence should be addressed. E-mail: ehrmann{at}cf.ac.uk.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: pre, premature; ss, signal sequenceless.
- Copyright © 2003, The National Academy of Sciences
