Loop diuretic and ion-binding residues revealed by scanning mutagenesis of transmembrane helix 3 (TM3) of Na-K-Cl cotransporter (NKCC1).

ABSTRACT: The Na-K-Cl cotransporter (NKCC) plays central roles in cellular chloride homeostasis and in epithelial salt transport, but to date little is known about the mechanism by which the transporter moves ions across the membrane. We examined the functional role of transmembrane helix 3 (TM3) in NKCC1 using cysteine- and tryptophan-scanning mutagenesis and analyzed our results in the context of a structural homology model based on an alignment of NKCC1 with other amino acid polyamine organocation superfamily members, AdiC and ApcT. Mutations of residues along one face of TM3 (Tyr-383, Met-382, Ala-379, Asn-376, Ala-375, Phe-372, Gly-369, and Ile-368) had large effects on translocation rate, apparent ion affinities, and loop diuretic affinity, consistent with a proposed role of TM3 in the translo

SUBMITTER: Somasekharan S 

PROVIDER: S-EPMC3366785 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature