3GIN

Crystal structure of E454K-CBD1

Summary for 3GIN

• Entry DOI: 10.2210/pdb3gin/pdb
• Related: 2DPK 2QVM
• Descriptor: Sodium/calcium exchanger 1, CALCIUM ION (3 entities in total)
• Functional Keywords: cbd1, cbd2, ncx, calcium binding domain 1, antiport, calcium transport, calmodulin-binding, cell membrane, glycoprotein, ion transport, membrane, phosphoprotein, sodium transport, transmembrane, transport, metal transport, metal binding protein
• Biological source: Canis lupus familiaris (dog)
• Cellular location: Cell membrane; Multi-pass membrane protein: P23685
• Total number of polymer chains: 2
• Total formula weight: 35204.91

Authors

Chaptal, V.,Mercado-Besserer, G.,Abramson, J. (deposition date: 2009-03-05, release date: 2009-04-21, Last modification date: 2024-11-27)

Primary citation

Chaptal, V.,Ottolia, M.,Mercado-Besserer, G.,Nicoll, D.A.,Philipson, K.D.,Abramson, J.
Structure and functional analysis of a Ca2+ sensor mutant of the na+/ca2+ exchanger
J.Biol.Chem., 284:14688-14692, 2009

PubMed 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.

PubMed: 19332552
DOI: 10.1074/jbc.C900037200

Experimental method

X-RAY DIFFRACTION (2.4 Å)