| First Author | Hilge M | Year | 2009 |
| Journal | Proc Natl Acad Sci U S A | Volume | 106 |
| Issue | 34 | Pages | 14333-8 |
| PubMed ID | 19667209 | Mgi Jnum | J:151940 |
| Mgi Id | MGI:4355610 | Doi | 10.1073/pnas.0902171106 |
| Citation | Hilge M, et al. (2009) Ca2+ regulation in the Na+/Ca2+ exchanger features a dual electrostatic switch mechanism. Proc Natl Acad Sci U S A 106(34):14333-8 |
| abstractText | Regulation of ion-transport in the Na(+)/Ca(2+) exchanger (NCX) occurs via its cytoplasmic Ca(2+)-binding domains, CBD1 and CBD2. Here, we present a mechanism for NCX activation and inactivation based on data obtained using NMR, isothermal titration calorimetry (ITC) and small-angle X-ray scattering (SAXS). We initially determined the structure of the Ca(2+)-free form of CBD2-AD and the structure of CBD2-BD that represent the two major splice variant classes in NCX1. Although the apo-form of CBD2-AD displays partially disordered Ca(2+)-binding sites, those of CBD2-BD are entirely unstructured even in an excess of Ca(2+). Striking differences in the electrostatic potential between the Ca(2+)-bound and -free forms strongly suggest that Ca(2+)-binding sites in CBD1 and CBD2 form electrostatic switches analogous to C(2)-domains. SAXS analysis of a construct containing CBD1 and CBD2 reveals a conformational change mediated by Ca(2+)-binding to CBD1. We propose that the electrostatic switch in CBD1 and the associated conformational change are necessary for exchanger activation. The response of the CBD1 switch to intracellular Ca(2+) is influenced by the closely located cassette exons. We further propose that Ca(2+)-binding to CBD2 induces a second electrostatic switch, required to alleviate Na(+)-dependent inactivation of Na(+)/Ca(2+) exchange. In contrast to CBD1, the electrostatic switch in CBD2 is isoform- and splice variant-specific and allows for tailored exchange activities. |
