DegP Chaperone Suppresses Toxic Inner Membrane Translocation Intermediates.
The periplasm of Gram-negative bacteria includes a variety of molecular chaperones that shepherd the folding and targeting of secreted proteins. A central player of this quality control network is DegP, a protease also suggested to have a chaperone function. We serendipitously discovered that production of the Bordetella pertussis autotransporter virulence protein pertactin is lethal in Escherichia coli ΔdegP strains. We investigated specific contributions of DegP to secretion of pertactin as a model system to test the functions of DegP in vivo. The DegP chaperone activity was sufficient to restore growth during pertactin production. This chaperone dependency could be relieved by changing the pertactin signal sequence: an E. coli signal sequence leading to co-translational inner membrane (IM) translocation was sufficient to suppress lethality in the absence of DegP, whereas an E. coli post-translational signal sequence was sufficient to recapitulate the lethal phenotype. These results identify a novel connection between the DegP chaperone and the mechanism used to translocate a protein across the IM. Lethality coincided with loss of periplasmic proteins, soluble σE, and proteins regulated by this essential stress response. These results suggest post-translational IM translocation can lead to the formation of toxic periplasmic folding intermediates, which DegP can suppress.
Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America.
Esther
E
Braselmann
Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America.
Julie L
JL
Chaney
Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America.
Matthew M
MM
Champion
Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America.|Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States of America.
Patricia L
http://orcid.org/0000-0001-5462-8248
PL
Clark
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000502:physiology*; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism / Q000502:physiology; D006360:Heat-Shock Proteins / Q000502:physiology*; D013058:Mass Spectrometry; D018832:Molecular Chaperones / Q000378:metabolism / Q000502:physiology; D033903:Periplasmic Proteins / Q000502:physiology*; D012697:Serine Endopeptidases / Q000502:physiology*; D000069320:Type V Secretion Systems / Q000378:metabolism / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D033903:Periplasmic Proteins; D000069320:Type V Secretion Systems; D010566:Virulence Factors, Bordetella; C068929:pertactin; C061682:DegP protease; D012697:Serine Endopeptidases