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Conformational dynamics of protein transporter FhaC : large‐scale motions of plug helix
Author(s) -
Guérin Jérémy,
Baud Catherine,
Touati Nadia,
Saint Nathalie,
Willery Eve,
Locht Camille,
Vezin Hervé,
JacobDubuisson Françoise
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12585
Subject(s) - periplasmic space , biology , secretion , bacterial outer membrane , transmembrane domain , transporter , transport protein , transmembrane protein , biophysics , helix (gastropod) , membrane transport protein , protein structure , protein dynamics , microbiology and biotechnology , biochemistry , membrane , escherichia coli , gene , ecology , receptor , snail
Summary FhaC is an integral outer membrane protein of the whooping cough agent B ordetella pertussis that mediates the transport to the cell surface of a major virulence factor, the filamentous haemagglutinin adhesin FHA . The FHA / FhaC pair is a prototypic TpsA / TpsB system of the widespread ‘Two‐Partner Secretion’ pathway, dedicated to the transport of long extracellular proteins in various pathogenic and environmental Gram‐negative bacteria. FhaC belongs to the ubiquitous Omp85 superfamily of protein transporters. The X ‐ray structure of FhaC shows that the transmembrane β‐barrel channel hypothesized to serve as the FHA ‐conducting pore is obstructed by two structural elements conserved among TpsB transporters, an N ‐terminal α helix and an extracellular loop. Here, we provide evidence for conformational dynamics of FhaC related to the secretion mechanism. Using paramagnetic electron resonance, electrophysiology and in vivo approaches, we showed that FhaC exchanges between open and closed conformations. The interaction with its secretory partner FHA alters this distribution of conformations. The open conformation of FhaC implies a large displacement from the channel of the N ‐terminal ‘plug’ helix, which remains in the periplasm during FHA secretion. The membrane environment favours the dynamics of the TpsB transporter.