PDBsum entry 1c7w

Metal binding protein

PDB id: 1c7w

Contents

Protein chain

68 a.a. *

* Residue conservation analysis

References listed in PDB file

Key reference

• Title: Sequential calcium binding to the regulatory domain of calcium vector protein reveals functional asymmetry and a novel mode of structural rearrangement.
• Authors: I.Théret, S.Baladi, J.A.Cox, H.Sakamoto, C.T.Craescu.
• Ref.: Biochemistry, 2000, 39, 7920-7926. [DOI no: 10.1021/bi000360z]
• PubMed id: 10891072

Abstract

Calcium vector protein (CaVP) from amphioxus is a two-domain, calcium-binding protein (18.3 kDa) of the calmodulin superfamily. Only two of the four EF-hand motifs (sites III and IV) have a significant binding affinity for calcium ions. We determined the solution structure of the domain containing these active sites (C-CaVP: W81-S161), in the Ca(2+)-saturated state, using NMR spectroscopy and restrained molecular dynamics. The tertiary structure is similar to other Ca(2+)-binding domains containing a pair of EF-hand motifs. The apo state has spectroscopic and thermodynamic characteristics of a molten globule, with conserved secondary structure but highly fluctuating tertiary organization. Titration of C-CaVP with Ca(2+) revealed a stepwise ion binding, with a stable equilibrium intermediate in which only site III binds a calcium ion. Despite a highly fluctuating structure of the free site IV, the calcium-bound site III has a persistent structure, with similar secondary elements but different interhelix angle and hydrophobic packing relative to the fully calcium-saturated state.