title: The dimerization equilibrium of a ClC Cl(-)/H(+) antiporter in lipid bilayers.
abstract: Interactions between membrane protein interfaces in lipid bilayers play an important role in membrane protein folding but quantification of the strength of these interactions has been challenging. Studying dimerization of ClC-type transporters offers a new approach to the problem, as individual subunits adopt a stable and functionally verifiable fold that constrains the system to two states - monomer or dimer. Here, we use single-molecule photobleaching analysis to measure the probability of ClC-ec1 subunit capture into liposomes during extrusion of large, multilamellar membranes. The capture statistics describe a monomer to dimer transition that is dependent on the subunit/lipid mole fraction density and follows an equilibrium dimerization isotherm. This allows for the measurement of the free energy of ClC-ec1 dimerization in lipid bilayers, revealing that it is one of the strongest membrane protein complexes measured so far, and introduces it as new type of dimerization model to investigate the physical forces that drive membrane protein association in membranes.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Rahul
authors.initials: R
authors.lastname: Chadda
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Venkatramanan
authors.initials: V
authors.lastname: Krishnamani
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Kacey
authors.initials: K
authors.lastname: Mersch
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.|Department of Natural Sciences, University of Bath, Bath, United Kingdom.
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Marley
authors.initials: M
authors.lastname: Brimberry
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Ankita
authors.initials: A
authors.lastname: Chadda
authors.affiliation: Department of Biochemistry, Brandeis University, Waltham, United States.
authors.forename: Ludmila
authors.initials: L
authors.lastname: Kolmakova-Partensky
authors.affiliation: Department of Biochemistry, Brandeis University, Waltham, United States.
authors.forename: Larry J
authors.identifier: 0000-0003-4946-8731
authors.initials: LJ
authors.lastname: Friedman
authors.affiliation: Department of Biochemistry, Brandeis University, Waltham, United States.
authors.forename: Jeff
authors.identifier: 0000-0001-7910-3421
authors.initials: J
authors.lastname: Gelles
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, United States.
authors.forename: Janice L
authors.identifier: 0000-0002-5499-9943
authors.initials: JL
authors.lastname: Robertson
mesh_terms: D018118:Chloride Channels / Q000378:metabolism*; D008051:Lipid Bilayers; D055503:Protein Multimerization; D000072760:Single Molecule Imaging
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D008051:Lipid Bilayers
keywords: E. coli; TIRF; biochemistry; biophysics; equilibrium; lipid bilayer; membrane protein; protein folding; single-molecule; structural biology