Open AccessStructures of the peptidase-containing ABC transporter PCAT1 under equilibrium and nonequilibrium conditions
Author(s) -
Virapat Kieuvongngam,
Jue Chen
Publication year - 2022
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.2120534119
Subject(s) - atp binding cassette transporter , atp hydrolysis , chemistry , transporter , dimer , transmembrane protein , transmembrane domain , nucleotide , biophysics , stereochemistry , enzyme , biochemistry , membrane , atpase , biology , receptor , organic chemistry , gene
Significance Recent advances in cryo-electron microscopy (cryo-EM) enabled us to determine multiple structures from the same sample. At equilibrium, the Boltzmann distribution law can be applied to identify the lowest energy state of the protein. We found that the conformational distributions of PCAT1, the peptidase-containing ATP-binding cassette (ABC) transporter 1, are completely different in the presence and absence of the Mg2+ ion. This difference reflects energy inflow from ATP hydrolysis, shifting the system out of equilibrium. The conformational distribution under ATP turnover condition is determined by the transition rates along the transport pathway rather than the energy of each state. This study demonstrates how cryo-EM data can be used to understand thermodynamic and kinetic properties of an active transporter.