Obligate coupling of CFTR pore opening to tight nucleotide-binding domain dimerization.
In CFTR, the chloride channel mutated in cystic fibrosis (CF) patients, ATP-binding-induced dimerization of two cytosolic nucleotide binding domains (NBDs) opens the pore, and dimer disruption following ATP hydrolysis closes it. Spontaneous openings without ATP are rare in wild-type CFTR, but in certain CF mutants constitute the only gating mechanism, stimulated by ivacaftor, a clinically approved CFTR potentiator. The molecular motions underlying spontaneous gating are unclear. Here we correlate energetic coupling between residues across the dimer interface with spontaneous pore opening/closure in single CFTR channels. We show that spontaneous openings are also strictly coupled to NBD dimerization, which may therefore occur even without ATP. Coordinated NBD/pore movements are therefore intrinsic to CFTR: ATP alters the stability, but not the fundamental structural architecture, of open- and closed-pore conformations. This explains correlated effects of phosphorylation, mutations, and drugs on ATP-driven and spontaneous activity, providing insights for understanding CF mutation and drug mechanisms.
Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary.|MTA-SE Ion Channel Research Group, Semmelweis University, Budapest, Hungary.
Csaba
0000-0001-7536-3066
C
Mihályi
Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary.|MTA-SE Ion Channel Research Group, Semmelweis University, Budapest, Hungary.
Beáta
B
Töröcsik
Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary.|MTA-SE Ion Channel Research Group, Semmelweis University, Budapest, Hungary.
László
0000-0002-6547-5889
L
Csanády
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D011487:Protein Conformation; D000072417:Protein Domains; D014981:Xenopus; D015053:Zygote / Q000378:metabolism
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate
ABC protein; E. coli; biochemistry; biophysics; conformation; mutant cycle; structural biology; structure; thermodynamic coupling; xenopus