2bl0
From Proteopedia
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PHYSARUM POLYCEPHALUM MYOSIN II REGULATORY DOMAIN
Overview
We have previously identified a single inhibitory Ca2+-binding site in the, first EF-hand of the essential light chain of Physarum conventional myosin, (Farkas, L., Malnasi-Csizmadia, A., Nakamura, A., Kohama, K., and Nyitray, L. (2003) J. Biol. Chem. 278, 27399-27405). As a general rule, conformation of the EF-hand-containing domains in the calmodulin family is, "closed" in the absence and "open" in the presence of bound cations; a, notable exception is the unusual Ca2+-bound closed domain in the essential, light chain of the Ca2+-activated scallop muscle myosin. Here we have, reported the 1.8 A resolution structure of the regulatory domain (RD) of, Physarum myosin II in which Ca2+ is bound to a canonical EF-hand that is, also in a closed state. The 12th position of the EF-hand loop, which, normally provides a bidentate ligand for Ca2+ in the open state, is too, far in the structure to participate in coordination of the ion. The, structure includes a second Ca2+ that only mediates crystal contacts. To, reveal the mechanism behind the regulatory effect of Ca2+, we compared, conformational flexibilities of the liganded and unliganded RD. Our, working hypothesis, i.e. the modulatory effect of Ca2+ on conformational, flexibility of RD, is in line with the observed suppression of, hydrogen-deuterium exchange rate in the Ca2+-bound form, as well as with, results of molecular dynamics calculations. Based on this evidence, we, concluded that Ca2+-induced change in structural dynamics of RD is a major, factor in Ca2+-mediated regulation of Physarum myosin II activity.
About this Structure
2BL0 is a Protein complex structure of sequences from Physarum polycephalum with CA as ligand. Active as Transferred entry: 3.6.4.1, with EC number 3.6.1.32 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Structural evidence for non-canonical binding of Ca2+ to a canonical EF-hand of a conventional myosin., Debreczeni JE, Farkas L, Harmat V, Hetenyi C, Hajdu I, Zavodszky P, Kohama K, Nyitray L, J Biol Chem. 2005 Dec 16;280(50):41458-64. Epub 2005 Oct 13. PMID:16227209
Page seeded by OCA on Tue Dec 18 18:50:44 2007
