Molecular determinants of allosteric regulation in NCX proteins.

摘要: Allosteric activation of NCX involves the binding cytosolic Ca2+ to regulatory domains CBD1 and CBD2. Previous studies with isolated CBD12 full-size identified synergistic interactions between two CBD that modify affinity kinetic properties sensing, although it remains unclear how Ca2+-binding signal is decoded propagates transmembrane domains. Biophysical analyses (X-ray, SAXS, stopped-flow techniques) preparations CBD1, CBD2, have shown Ca3-Ca4 sites results in interdomain tethering CBDs through specific amino acids on (Asp499 Asp500) CBD2 (Arg532 Asp565). Mutant suggest two-domain interface governs Ca2+-driven conformational alignment CBDs, resulting slow dissociation from CBD12, thus, mediates Ca2+-induced transitions associated allosteric transmission. Specifically, occupation by induces disorder-to-order transition owing charge neutralization coordination, thereby constraining freedom, rigidifying NCX1 f-loop, triggering transmission membrane domain. The newly found switch highly conserved among isoform/splice variants, some additional structural motifs may shape specificity variants.