Structural basis for calmodulin as a dynamic calcium sensor.Zhang, M., Abrams, C., Wang, L., Gizzi, A., He, L., Lin, R., Chen, Y., Loll, P.J., Pascal, J.M., Zhang, J.F.
(2012) Structure 20: 911-923
- PubMed: 22579256
- DOI: https://doi.org/10.1016/j.str.2012.03.019
- Primary Citation of Related Structures:
- PubMed Abstract:
Calmodulin is a prototypical and versatile Ca(2+) sensor with EF hands as its high-affinity Ca(2+) binding domains. Calmodulin is present in all eukaryotic cells, mediating Ca(2+)-dependent signaling. Upon binding Ca(2+), calmodulin changes its conformation to form complexes with a diverse array of target proteins. Despite a wealth of knowledge on calmodulin, little is known on how target proteins regulate calmodulin's ability to bind Ca(2+). Here, we take advantage of two splice variants of SK2 channels, which are activated by Ca(2+)-bound calmodulin but show different sensitivity to Ca(2+) for their activation. Protein crystal structures and other experiments show that, depending on which SK2 splice variant it binds to, calmodulin adopts drastically different conformations with different affinities for Ca(2+) at its C-lobe. Such target protein-induced conformational changes make calmodulin a dynamic Ca(2+) sensor capable of responding to different Ca(2+) concentrations in cellular Ca(2+) signaling.
Department of Molecular Physiology and Biophysics, Jefferson Medical College, Philadelphia, PA 19107, USA.