This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
2bl0
From Proteopedia
|
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 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 Sun Feb 3 10:25:19 2008
