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Cell. 2015 Oct 22;163(3):724-33. doi: 10.1016/j.cell.2015.09.052. Epub 2015 Oct 22.

Timing of CFTR pore opening and structure of its transition state.

Author information

1
Department of Medical Biochemistry, Semmelweis University, Tűzoltó u. 37-47, Budapest 1094, Hungary; MTA-SE Ion Channel Research Group, Semmelweis University, Tűzoltó u. 37-47, Budapest 1094, Hungary.
2
MTA-SE Ion Channel Research Group, Semmelweis University, Tűzoltó u. 37-47, Budapest 1094, Hungary.
3
Department of Medical Biochemistry, Semmelweis University, Tűzoltó u. 37-47, Budapest 1094, Hungary; MTA-SE Ion Channel Research Group, Semmelweis University, Tűzoltó u. 37-47, Budapest 1094, Hungary. Electronic address: csanady.laszlo@med.semmelweis-univ.hu.

Abstract

In CFTR, the chloride ion channel mutated in cystic fibrosis (CF) patients, pore opening is coupled to ATP-binding-induced dimerization of two cytosolic nucleotide binding domains (NBDs) and closure to dimer disruption following ATP hydrolysis. CFTR opening rate, unusually slow because of its high-energy transition state, is further slowed by CF mutation ΔF508. Here, we exploit equilibrium gating of hydrolysis-deficient CFTR mutant D1370N and apply rate-equilibrium free-energy relationship analysis to estimate relative timing of opening movements in distinct protein regions. We find clear directionality of motion along the longitudinal protein axis and identify an opening transition-state structure with the NBD dimer formed but the pore still closed. Thus, strain at the NBD/pore-domain interface, the ΔF508 mutation locus, underlies the energetic barrier for opening. Our findings suggest a therapeutic opportunity to stabilize this transition-state structure pharmacologically in ΔF508-CFTR to correct its opening defect, an essential step toward restoring CFTR function.

PMID:
26496611
DOI:
10.1016/j.cell.2015.09.052
[Indexed for MEDLINE]
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