NMR Research Today is a free monthly online journal that collates and summarizes the latest research about NMR, including details on nuclear magnetic resonance, structural determination, techniques.

NMR analysis of the Mg2+-binding properties of aequorin, a Ca2+-binding photoprotein.

Ohashi W, Inouye S, Yamazaki T, Hirota H

RIKEN Genomic Sciences Center, 1-7-22, Suehiro, Tsurumi, Yokohama 230-0045.

Aequorin, which is a calcium-sensitive photoprotein and a member of the EF-hand superfamily, binds to Mg2+ under physiological conditions, which modulates its light emission. The Mg2+ binding site and its stabilizing influence were examined by NMR spectroscopy. The binding of Mg2+ to aequorin prevented the molecule from aggregating and stabilized it in the monomeric form. To determine the structural differences between Mg2+-bound and free aequorin, we have performed backbone NMR assignments of aequorin in the Mg2+-free state. Mg2+ binding induces conformational changes that are localized in the EF-hand loops. The chemical shift difference data indicated that there are two Mg2+-binding sites, EF-hands I and III. The Mg2+ titration experiment revealed that EF-hand III binds to Mg2+ with higher affinity than EF-hand I, and that only EF-hand III seems to be occupied by Mg2+ under physiological conditions.

Published 7 November 2005 in J Biochem (Tokyo), 138(5): 613-20.
Full-text of this article is available online (may require subscription).

© 2005-2008 NMR Research Today. All Rights Reserved.