Vectorial transport and folding of an autotransporter virulence protein during outer membrane secretion.
Autotransporter (AT) proteins are a large and diverse family of extracellular virulence proteins from Gram-negative bacteria, characterized by a central beta-helix domain within the mature virulence protein. It is not clear how these proteins cross the outer membrane (OM) quickly and efficiently, without assistance from an external energy source such as ATP or a proton gradient. Conflicting results in the literature have led to several proposed mechanisms for AT OM secretion, including a concerted process, or vectorial secretion with different directionalities. We introduced pairs of cysteine residues into the passenger sequence of pertactin, an AT virulence protein from Bordetella pertussis, and show that OM secretion of the passenger domain stalls due to the formation of a disulphide bond. We further show that the C-terminus of the pertactin passenger domain beta-helix crosses the OM first, followed by the N-terminal portions of the virulence protein. In vivo proteolytic digestion shows that the C-terminus is exposed to the extracellular milieu during stalling, and forms stable structure. These AT secretion and folding features can potentially facilitate efficient secretion.
Junker
Mirco
M
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
Besingi
Richard N
RN
Clark
Patricia L
PL
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001886:Bordetella pertussis / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D010566:Virulence Factors, Bordetella / Q000235:genetics / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D026901:Membrane Transport Proteins; D010566:Virulence Factors, Bordetella; C068929:pertactin