PDBsum entry 3jtd

Contractile protein

PDB id: 3jtd

Contents

Protein chains

65 a.a. *

156 a.a. *

156 a.a. *

Metals

_MG

Waters ×58

* Residue conservation analysis

PDB id:

3jtd

Name:

Contractile protein

Title:

Calcium-free scallop myosin regulatory domain with elc-d19a point mutation

Structure:

Myosin heavy chain, striated adductor muscle. Chain: a. Myosin regulatory light chain, striated adductor muscle. Chain: b. Synonym: r-lc. Myosin essential light chain, striated adductor muscle. Chain: c. Synonym: e-lc, sulfhydryl light chain, shlc. Engineered: yes.

Source:

Argopecten irradians. Bay scallop. Organism_taxid: 31199. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

2.57Å R-factor: 0.233 R-free: 0.248

Authors:

D.M.Himmel,S.Mui,E.O'Neall-Hennessey,A.Szent-Gyorgyi,C.Cohen

Key ref:

D.M.Himmel et al. (2009). The on-off switch in regulated myosins: different triggers but related mechanisms. J Mol Biol, 394, 496-505. PubMed id: 19769984 DOI: 10.1016/j.jmb.2009.09.035

Date:

11-Sep-09 Release date: 01-Dec-09

Protein chain

P24733  (MYS_ARGIR) -  Myosin heavy chain, striated muscle from Argopecten irradians

Seq: 1938 a.a.

Struc: 65 a.a.

Protein chain

P13543  (MLR_ARGIR) -  Myosin regulatory light chain, striated adductor muscle from Argopecten irradians

Seq: 157 a.a.

Struc: 156 a.a.

Protein chain

P07291  (MLE_ARGIR) -  Myosin essential light chain, striated adductor muscle from Argopecten irradians

Seq: 157 a.a.

Struc: 156 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1016/j.jmb.2009.09.035

J Mol Biol 394:496-505 (2009)

PubMed id: 19769984

The on-off switch in regulated myosins: different triggers but related mechanisms.

D.M.Himmel, S.Mui, E.O'Neall-Hennessey, A.G.Szent-Györgyi, C.Cohen.

ABSTRACT

In regulated myosin, motor and enzymatic activities are toggled between the on-state and off-state by a switch located on its lever arm domain, here called the regulatory domain (RD). This region consists of a long alpha-helical "heavy chain" stabilized by a "regulatory" light chain (RLC) and an "essential" light chain (ELC). The on-state is activated by phosphorylation of the RLC of vertebrate smooth muscle RD or by direct binding of Ca(2+) to the ELC of molluscan RD. Crystal structures are available only for the molluscan RD. To understand in more detail the pathway between the on-state and the off-state, we have now also determined the crystal structure of a molluscan (scallop) RD in the absence of Ca(2+). Our results indicate that loss of Ca(2+) abolishes most of the interactions between the light chains and may increase the flexibility of the RD heavy chain. We propose that disruption of critical links with the C-lobe of the RLC is the key event initiating the off-state in both smooth muscle myosins and molluscan myosins.

Selected figure(s)

Figure 3.
Fig. 3. Ca^2+ binding stabilizesHC/RLC/ELC interactions in scallop structures. (a) Shown is a vast hydrogen-bond and covalent-bond network in the Ca^2+-RD structure extending from the Ca^2+ binding site to Lys149 on the RLC N-lobe. (b) Part of this network forms a meshwork that stabilizes the coordination of Ca^2+, shown here schematically. Solid gray lines indicate main-chain interactions, and wavy lines indicate side-chain interactions. (c) The same meshwork as (b) in the absence of Ca^2+. Notice that when the Gly23 carbonyl rotates away from the Ca^2+ binding site, four hydrogen bonds from this meshwork are abolished.

Figure 5.
Fig. 5. Scallop and squid RLC. Scallop (color) and squid (gray tones; PDB code 2OVK)^30 are superposed (superposition based on scallop HC residues 807–818 and equivalent squid HC residues 809–820). The scallop structure is shown oriented as in Fig. 4. In the squid crystal structure, the RLC N-lobe is rotated closer to the C-lobe, bringing helix A and the RLC N-terminus within reach of helices E and H. RLC residue C^α distances are shown (in Å) for scallop Asp84-Lys149 (magenta), scallop Pro13-Asp84 (tan), and squid Arg13-Glu84 (black).

The above figures are reprinted by permission from Elsevier: J Mol Biol (2009, 394, 496-505) copyright 2009.

Figures were selected by an automated process.