PDBsum entry 2kls

Metal binding protein

PDB id: 2kls

Contents

Protein chain

157 a.a. *

* Residue conservation analysis

PDB id:

2kls

Name:

Metal binding protein

Title:

Apo-form of the second ca2+ binding domain of ncx1.4

Structure:

Sodium/calcium exchanger 1. Chain: a. Fragment: second ca2+ binding domain. Synonym: na(+)/ca(2+)-exchange protein 1. Engineered: yes

Source:

Canis familiaris. Dog. Organism_taxid: 9615. Gene: slc8a1. Expressed in: escherichia coli. Expression_system_taxid: 562. Expression_system_variant: de3.

NMR struc:

20 models

Authors:

M.Hilge,J.Aelen,A.Foarce,A.Perrakis,G.W.Vuister

Key ref:

M.Hilge et al. (2009). Ca2+ regulation in the Na+/Ca2+ exchanger features a dual electrostatic switch mechanism. Proc Natl Acad Sci U S A, 106, 14333-14338. PubMed id: 19667209

Date:

08-Jul-09 Release date: 18-Aug-09

Protein chain

No UniProt id for this chain

Struc: 157 a.a.

Proc Natl Acad Sci U S A 106:14333-14338 (2009)

PubMed id: 19667209

Ca2+ regulation in the Na+/Ca2+ exchanger features a dual electrostatic switch mechanism.

M.Hilge, J.Aelen, A.Foarce, A.Perrakis, G.W.Vuister.

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.