2KLT

Second Ca2+ binding domain of NCX1.3

Summary for 2KLT

• Entry DOI: 10.2210/pdb2klt/pdb
• Related: 2kls
• Descriptor: Sodium/calcium exchanger 1 (1 entity in total)
• Functional Keywords: sodium calcium exchanger, electrostatic switch, ca2+ sensor, ca2+ regulation, metal binding protein
• Biological source: Canis familiaris (Dog)
• Total number of polymer chains: 1
• Total formula weight: 18799.06

Authors

Hilge, M.,Aelen, J.,Foarce, A.,Perrakis, A.,Vuister, G.W. (deposition date: 2009-07-08, release date: 2009-08-18, Last modification date: 2024-05-22)

Primary citation

Hilge, M.,Aelen, J.,Foarce, A.,Perrakis, A.,Vuister, G.W.
Ca2+ regulation in the Na+/Ca2+ exchanger features a dual electrostatic switch mechanism.
Proc.Natl.Acad.Sci.USA, 106:14333-14338, 2009

PubMed Abstract: 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.

PubMed: 19667209
DOI: 10.1073/pnas.0902171106

Experimental method

SOLUTION NMR