ABCMdb

PMID: 20110677

Kloch M, Milewski M, Nurowska E, Dworakowska B, Cutting GR, Dolowy K
The H-loop in the second nucleotide-binding domain of the cystic fibrosis transmembrane conductance regulator is required for efficient chloride channel closing.
Cell Physiol Biochem. 2010;25(2-3):169-80. Epub 2010 Jan 12., [PubMed]

Sentences

No. Mutations Sentence Comment

30 ABCC7 p.His1402Ala ABCC7 p.Arg1403Ala Mutations within the H-loop of NBD2, including the deletion of the entire ag region (Δ1395-1403) and the double alanine substitution H1402A, R1403A (HR→AA), were created in the CFTR-containing pBQ4.7 vector (a gift from J. Rommens and L.-C. Tsui) using the site-directed mutagenesis system "Transformer" (Becton Dickinson). Login to comment 195 ABCC7 p.Glu1371Ser ABCC7 p.Glu1371Gln Substitution of this conserved glutamate with either serine (E1371S) or glutamine (E1371Q) produces a channel that displays prolonged open times [3, 16, 21, 59]. Login to comment 196 ABCC7 p.Glu1371Gln Importantly, a recent study has demonstrated that the E1371Q substitution leads to significant decrease ofATPase activity in the full-length CFTR [50] and an earlier study has shown that the same mutation abolishes the ATPase activity of the NBD1-NBD2 heterodimer, while not affecting the nucleotide binding affinity of NBD2 [49]. Login to comment 197 ABCC7 p.Glu1371Gln Hence, although we have no data regarding the influence of E1371Q on the CFTR opening rate, it seems that mutations affecting either the H-loop or Glu1371 have a very similar impact on ATP-dependent CFTR gating, which suggests close cooperation of both these elements, as predicted in the catalytic dyad model. Login to comment 207 ABCC7 p.Glu1401Lys Similar decrease in whole-cell currents has been very recently reported for another H-loop mutation E1401K, associated with CBAVD [66].The above results may seem surprising in light of our finding that the HR→AA CFTR mutant shows increased open probability in single-channel analysis (Fig. 3A). Login to comment