Channel properties of TpsB transporter FhaC point to two functional domains with a C-terminal protein-conducting pore.
Integral outer membrane transporters of the Omp85/TpsB superfamily mediate the translocation of proteins across, or their integration into, the outer membranes of Gram-negative bacteria, chloroplasts, and mitochondria. The Bordetella pertussis FhaC/FHA couple serves as a model for the two-partner secretion pathway in Gram-negative bacteria, with the TpsB protein, FhaC, being the specific transporter of its TpsA partner, FHA, across the outer membrane. In this work, we have investigated the structure/function relationship of FhaC by analyzing the ion channel properties of the wild type protein and a collection of mutants with varied FHA secretion activities. We demonstrated that the channel is formed by the C-terminal two-thirds of FhaC most likely folding into a beta-barrel domain predicted to be conserved throughout the family. A C-proximal motif that represents the family signature appears essential for pore function. The N-terminal 200 residues of FhaC constitute a functionally distinct domain that modulates the pore properties and may participate in FHA recognition.
Méli
Albano C
AC
UMR 5048 CNRS, U554 INSERM, Centre de Biochimie Structurale, 29 Rue de Navacelles, 34090 Montpellier Cedex, France.
Hodak
Hélène
H
Clantin
Bernard
B
Locht
Camille
C
Molle
Gérard
G
Jacob-Dubuisson
Françoise
F
Saint
Nathalie
N
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D001886:Bordetella pertussis / Q000235:genetics / Q000378:metabolism*; D007477:Ions / Q000378:metabolism; D008051:Lipid Bilayers; D008564:Membrane Potentials / Q000502:physiology; D016296:Mutagenesis; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D007477:Ions; D008051:Lipid Bilayers; C098052:fhaC protein, Bordetella pertussis