2ccm

From Proteopedia

Revision as of 17:07, 18 December 2007

X-RAY STRUCTURE OF CALEXCITIN FROM LOLIGO PEALEII AT 1.8A

Overview

The three-dimensional structure of the neuronal calcium-sensor protein, calexcitin from Loligo pealei has been determined by X-ray analysis at a, resolution of 1.8A. Calexcitin is up-regulated following Pavlovian, conditioning and has been shown to regulate potassium channels and the, ryanodine receptor. Thus, calexcitin is implicated in neuronal excitation, and plasticity. The overall structure is predominantly helical and compact, with a pronounced hydrophobic core between the N and C-terminal domains of, the molecule. The structure consists of four EF-hand motifs although only, the first three EF hands are involved in binding calcium ions; the, C-terminal EF-hand lacks the amino acids required for calcium binding. The, overall structure is quite similar to that of the sarcoplasmic, calcium-binding protein from Amphioxus although the sequence identity is, very low at 31%. The structure shows that the two amino acids of, calexcitin phosphorylated by protein kinase C are close to the domain, interface in three dimensions and thus phosphorylation is likely to, regulate the opening of the domains that is probably required for binding, to target proteins. There is evidence that calexcitin is a GTPase and the, residues, which have been implicated by mutagenesis in its GTPase, activity, are in a short but highly conserved region of 3(10) helix close, to the C terminus. This helix resides in a large loop that is partly, sandwiched between the N and C-terminal domains suggesting that GTP, binding may also require or may cause domain opening. The structure, possesses a pronounced electropositive crevice in the vicinity of the, 3(10) helix, that might provide an initial docking site for the, triphosphate group of GTP. These findings elucidate a number of the, reported functions of calexcitin with implications for neuronal, signalling.

About this Structure

2CCM is a Single protein structure of sequence from Loligo plei with CA as ligand. Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Structure of the neuronal protein calexcitin suggests a mode of interaction in signalling pathways of learning and memory., Erskine PT, Beaven GD, Hagan R, Findlow IS, Werner JM, Wood SP, Vernon J, Giese KP, Fox G, Cooper JB, J Mol Biol. 2006 Apr 14;357(5):1536-47. Epub 2006 Feb 8. PMID:16497326

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