5F6T

Structure of calexcitin-Gd3+ complex.

Summary for 5F6T

• Entry DOI: 10.2210/pdb5f6t/pdb
• Related: 2ccm
• Descriptor: Calexcitin, GADOLINIUM ATOM, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: ef-hand neuronal calcium signalling, calcium-binding protein
• Biological source: Doryteuthis pealeii (Longfin inshore squid)
• Total number of polymer chains: 1
• Total formula weight: 22538.47

Authors

Chataigner, L.,Guo, J.,Erskine, P.T.,Coker, A.R.,Wood, S.P.,Cooper, J.B. (deposition date: 2015-12-06, release date: 2015-12-16, Last modification date: 2024-01-10)

Primary citation

Chataigner, L.,Guo, J.,Erskine, P.T.,Coker, A.R.,Wood, S.P.,Gombos, Z.,Cooper, J.B.
Binding of Gd(3+) to the neuronal signalling protein calexcitin identifies an exchangeable Ca(2+)-binding site.
Acta Crystallogr.,Sect.F, 72:276-281, 2016

PubMed Abstract: Calexcitin was first identified in the marine snail Hermissenda crassicornis as a neuronal-specific protein that becomes upregulated and phosphorylated in associative learning. Calexcitin possesses four EF-hand motifs, but only the first three (EF-1 to EF-3) are involved in binding metal ions. Past work has indicated that under physiological conditions EF-1 and EF-2 bind Mg(2+) and Ca(2+), while EF-3 is likely to bind only Ca(2+). The fourth EF-hand is nonfunctional owing to a lack of key metal-binding residues. The aim of this study was to use a crystallographic approach to determine which of the three metal-binding sites of calexcitin is most readily replaced by exogenous metal ions, potentially shedding light on which of the EF-hands play a `sensory' role in neuronal calcium signalling. By co-crystallizing recombinant calexcitin with equimolar Gd(3+) in the presence of trace Ca(2+), EF-1 was shown to become fully occupied by Gd(3+) ions, while the other two sites remain fully occupied by Ca(2+). The structure of the Gd(3+)-calexcitin complex has been refined to an R factor of 21.5% and an Rfree of 30.4% at 2.2 Å resolution. These findings suggest that EF-1 of calexcitin is the Ca(2+)-binding site with the lowest selectivity for Ca(2+), and the implications of this finding for calcium sensing in neuronal signalling pathways are discussed.

PubMed: 27050260
DOI: 10.1107/S2053230X16003526

Experimental method

X-RAY DIFFRACTION (2.201 Å)