SecA-dependent quality control of intracellular protein localization.
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.
Eser
Markus
M
School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, United Kingdom.
Ehrmann
Michael
M
D000251:Adenosine Triphosphatases / Q000378:metabolism / Q000502:physiology*; D000469:Alkaline Phosphatase; D000681:Amylases / Q000737:chemistry; D001426:Bacterial Proteins; D002950:Citrate (si)-Synthase / Q000737:chemistry; D018844:Cyclin-Dependent Kinases / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D017510:Protein Folding; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013696:Temperature; D013997:Time Factors
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D002950:Citrate (si)-Synthase; D018844:Cyclin-Dependent Kinases; D000469:Alkaline Phosphatase; C114089:phoA protein, E coli; D000681:Amylases; C108136:MalS protein, E coli; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins