PDBsum entry: 3gin

Metal binding protein

PDB id: 3gin

Contents

Protein chains

116 a.a. *

Metals

_CA ×7

Waters ×98

* Residue conservation analysis

PDB id:

3gin

Name:

Metal binding protein

Title:

Crystal structure of e454k-cbd1

Structure:

Sodium/calcium exchanger 1. Chain: a, b. Fragment: calx-beta 1 domain. Synonym: na(+)/ca(2+)-exchange protein 1. Engineered: yes. Mutation: yes

Source:

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

Resolution:

2.40Å R-factor: 0.196 R-free: 0.259

Authors:

V.Chaptal,G.Mercado-Besserer,J.Abramson

Key ref:

V.Chaptal et al. (2009). Structure and functional analysis of a Ca2+ sensor mutant of the Na+/Ca2+ exchanger. J Biol Chem, 284, 14688-14692. PubMed id: 19332552 DOI: 10.1074/jbc.C900037200

Date:

05-Mar-09 Release date: 21-Apr-09

Protein chains

P23685  (NAC1_CANFA) -  Sodium/calcium exchanger 1

Seq: 970 a.a.

Struc: 116 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

 Gene Ontology (GO) functional annotation 

• Cellular component: integral to membrane (1 term)
• Biological process: cell communication (1 term)

DOI no: 10.1074/jbc.C900037200

J Biol Chem 284:14688-14692 (2009)

PubMed id: 19332552

Structure and functional analysis of a Ca2+ sensor mutant of the Na+/Ca2+ exchanger.

V.Chaptal, M.Ottolia, G.Mercado-Besserer, D.A.Nicoll, K.D.Philipson, J.Abramson.

ABSTRACT

The mammalian Na(+)/Ca(2+) exchanger, NCX1.1, serves as the main mechanism for Ca(2+) efflux across the sarcolemma following cardiac contraction. In addition to transporting Ca(2+), NCX1.1 activity is also strongly regulated by Ca(2+) binding to two intracellular regulatory domains, CBD1 and CBD2. The structures of both of these domains have been solved by NMR spectroscopy and x-ray crystallography, greatly enhancing our understanding of Ca(2+) regulation. Nevertheless, the mechanisms by which Ca(2+) regulates the exchanger remain incompletely understood. The initial NMR study showed that the first regulatory domain, CBD1, unfolds in the absence of regulatory Ca(2+). It was further demonstrated that a mutation of an acidic residue involved in Ca(2+) binding, E454K, prevents this structural unfolding. A contradictory result was recently obtained in a second NMR study in which Ca(2+) removal merely triggered local rearrangements of CBD1. To address this issue, we solved the crystal structure of the E454K-CBD1 mutant and performed electrophysiological analyses of the full-length exchanger with mutations at position 454. We show that the lysine substitution replaces the Ca(2+) ion at position 1 of the CBD1 Ca(2+) binding site and participates in a charge compensation mechanism. Electrophysiological analyses show that mutations of residue Glu-454 have no impact on Ca(2+) regulation of NCX1.1. Together, structural and mutational analyses indicate that only two of the four Ca(2+) ions that bind to CBD1 are important for regulating exchanger activity.

Selected figure(s)

Figure 1.
Structural comparison between WT-CBD1 (gray, PDB code: 2DPK) and E454K-CBD1 (blue). The three Ca^2+ ions bound to E454K-CBD1 are displayed as green spheres and numbered according to WT-CBD1 numbering (5). For clarity, the β strands are labeled A–G.

Figure 2.
Overlay of the Ca^2+ binding sites of WT-CBD1 and E454K-CBD1. E454K-CBD1 is shown as a blue drawing, and Ca^2+ ions are depicted as green spheres. Ca^2+-coordinating residues are displayed as sticks colored by atom type (Cα is yellow). Relevant metal ion coordinations and charge pairs of E454K-CBD1 are shown as black dotted lines. WT-CBD1 is shown as a gray drawing, and equivalent residues are displayed as sticks colored by atom type. Ca^2+ ions are numbered according to Ref. 5.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2009, 284, 14688-14692) copyright 2009.

Figures were selected by an automated process.