Structural evidence for non-canonical binding of Ca2+ to a canonical EF-hand of a conventional myosin

被引:18
作者
Debreczeni, JÉ
Farkas, L
Harmat, V
Hetényi, C
Hajdú, I
Závodszky, P
Kohama, K
Nyitray, L
机构
[1] Eotvos Lorand Univ, Dept Biochem, H-1117 Budapest, Hungary
[2] Eotvos Lorand Univ, Hungarian Acad Sci, Prot Modelling Grp, H-1117 Budapest, Hungary
[3] Gunma Univ, Dept Pharmacol, Maebashi, Gumma 3718510, Japan
[4] Hungarian Acad Sci, Biol Res Ctr, Inst Enzymol, H-1117 Budapest, Hungary
关键词
D O I
10.1074/jbc.M506315200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We have previously identified a single inhibitory Ca2+-binding site in the first EF-hand of the essential light chain of Physarum conventional myosin. 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 angstrom 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.
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页码:41458 / 41464
页数:7
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