PDBsum entry 2bl0

Muscle protein

PDB id: 2bl0

Contents

Protein chains

63 a.a. *

145 a.a. *

142 a.a. *

Metals

_CA ×2

Waters ×230

* Residue conservation analysis

PDB id:

2bl0

Name:

Muscle protein

Title:

Physarum polycephalum myosin ii regulatory domain

Structure:

Major plasmodial myosin heavy chain. Chain: a. Fragment: regulatory domain, residues 778-840. Synonym: physarum polycephalum myosin ii heavy chain. Engineered: yes. Myosin regulatory light chain. Chain: b. Fragment: regulatory domain, residues 1-145. Synonym: physarum polycephalum myosin ii essential light chain,

Source:

Physarum polycephalum. Organism_taxid: 5791. Expressed in: eschericia coli. Expression_system_taxid: 511693.

Biol. unit:

Trimer (from PDB file)

Resolution:

1.75Å R-factor: 0.221 R-free: 0.252

Authors:

J.E.Debreczeni,L.Farkas,V.Harmat,L.Nyitray

Key ref:

J.E.Debreczeni et al. (2005). Structural evidence for non-canonical binding of Ca2+ to a canonical EF-hand of a conventional myosin. J Biol Chem, 280, 41458-41464. PubMed id: 16227209 DOI: 10.1074/jbc.M506315200

Date:

23-Feb-05 Release date: 13-Oct-05

Protein chain

Q9BJD3  (Q9BJD3_PHYPO) -  Major plasmodial myosin heavy chain from Physarum polycephalum

Seq: 2148 a.a.

Struc: 63 a.a.

Protein chain

P08053  (MLR_PHYPO) -  Myosin regulatory light chain from Physarum polycephalum

Seq: 147 a.a.

Struc: 145 a.a.

Protein chain

Q8WSQ4  (Q8WSQ4_PHYPO) -  Myosin regulatory light chain from Physarum polycephalum

Seq: 157 a.a.

Struc: 142 a.a.

Enzyme reactions

• Enzyme class: Chains A, B, C: E.C.3.6.1.32 - Transferred entry: 5.6.1.8.

DOI no: 10.1074/jbc.M506315200

J Biol Chem 280:41458-41464 (2005)

PubMed id: 16227209

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

J.E.Debreczeni, L.Farkas, V.Harmat, C.Hetényi, I.Hajdú, P.Závodszky, K.Kohama, L.Nyitray.

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.

Selected figure(s)

Figure 2.
FIGURE 2. Structure and comparison of the Ca^2+ binding EF-hands of ELC and CaM. A, octahedral coordination of Ca^2+ ion in the first EF-hand of ELC showing an unusual closed conformation. Ca^2+ is coordinated by Asp-15, Asp-17, Asp-19, Lys-21, and two water molecules (red dots). Glu-26, which normally provides a bidentate ligand for Ca^2+ in the open state, is too far in the structure to participate in coordination of the ion. B, comparison of the Ca^2+ binding EF-hand I of the Physarum (red) and scallop myosins (blue; Protein Data Bank accession code 1wdc) and the mutant CaM structure (green; 1y6w) reveals high similarity between the Physarum and the mutant CaM structure. Note the extra turn in the first helix of scallop ELC. r.m.s. deviations of the backbone carbons, after superimposing the scallop and calmodulin structures, are 0.53 Å.

Figure 4.
FIGURE 4. Conformation of the heavy chain in the Physarum, scallop muscle and chicken skeletal muscle myosin RD, respectively. A least squares superposition of the long helical neck region from the Physarum (gray), scallop (blue; Protein Data Bank accession code 1wdc), and chicken (yellow; 2mys) myosins is shown. The Physarum RD shows the sharpest bend at the hook region (RLC interlobe interface) and the smallest bend at the ELC-RLC interface.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2005, 280, 41458-41464) copyright 2005.

Figures were selected by an automated process.