| Autor: |
Hilge, Mark, Aelen, Jan, Foarce, Alice, Perrakish, Anastassis, Vuister, Geerten W. |
| Předmět: |
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| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 8/25/2009, Vol. 106 Issue 34, p14333-14338, 6p, 5 Diagrams |
| Abstrakt: |
Regulation of ion-transport in the Na+/Ca2+ exchanger (NCX) occurs via its cytoplasmic Ca2+-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 Ca2+-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 Ca2+-binding sites, those of CBD2-BD are entirely unstructured even in an excess of Ca2+. Striking differences in the electrostatic potential between the Ca2+-bound and -free forms strongly suggest that Ca2+-binding sites in CBD1 and CBD2 form electrostatic switches analogous to C2-domains. SAXS analysis of a construct containing CBD1 and CBD2 reveals a conformational change mediated by Ca2+-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 Ca2+ is influenced by the closely located cassette exons. We further propose that Ca2+-binding to CBD2 induces a second electrostatic switch, required to alleviate Na+-dependent inactivation of Na+/Ca2+ exchange. In contrast to CBD1, the electrostatic switch in CBD2 is isoform- and splice variant-specific and allows for tailored exchange activities. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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