2BL0

Physarum polycephalum myosin II regulatory domain

Summary for 2BL0

• Entry DOI: 10.2210/pdb2bl0/pdb
• Descriptor: MAJOR PLASMODIAL MYOSIN HEAVY CHAIN, MYOSIN REGULATORY LIGHT CHAIN, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: muscle protein, slime mould, ef-hand, myosin
• Biological source: PHYSARUM POLYCEPHALUM; More
• Total number of polymer chains: 3
• Total formula weight: 39791.01

Authors

Debreczeni, J.E.,Farkas, L.,Harmat, V.,Nyitray, L. (deposition date: 2005-02-23, release date: 2005-10-13, Last modification date: 2024-05-08)

Primary citation

Debreczeni, J.E.,Farkas, L.,Harmat, V.,Hetenyi, C.,Hajdu, I.,Zavodszky, P.,Kohama, K.,Nyitray, L.
Structural Evidence for Non-Canonical Binding of Ca2+ to a Canonical EF-Hand of a Conventional Myosin.
J.Biol.Chem., 280:41458-, 2005

PubMed Abstract: 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.

PubMed: 16227209
DOI: 10.1074/JBC.M506315200

Experimental method

X-RAY DIFFRACTION (1.75 Å)