PDBsum entry 1i84

Contractile protein

PDB id: 1i84

Contents

Protein chains

909 a.a. *

148 a.a. *

138 a.a.* *

* Residue conservation analysis

* C-alpha coords only

PDB id:

1i84

Name:

Contractile protein

Title:

Cryo-em structure of the heavy meromyosin subfragment of chicken gizzard smooth muscle myosin with regulatory light chain in the dephosphorylated state. Only c alphas provided for regulatory light chain. Only backbone atoms provided for s2 fragment.

Structure:

Smooth muscle myosin heavy chain. Chain: s, v. Fragment: meromyosin subfragment. S1 and s2 fragments.. Synonym: myosin heavy chain, gizzard smooth muscle. Engineered: yes. Smooth muscle myosin essential light chain. Chain: t, w. Fragment: s1 fragment. Synonym: elc, myosin alkali light chain.

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108. Other_details: flag-tag at c-terminus.

Biol. unit:

Hexamer (from PQS)

Authors:

T.Wendt,D.Taylor,K.M.Trybus,K.Taylor

Key ref:

T.Wendt et al. (2001). Three-dimensional image reconstruction of dephosphorylated smooth muscle heavy meromyosin reveals asymmetry in the interaction between myosin heads and placement of subfragment 2. Proc Natl Acad Sci U S A, 98, 4361-4366. PubMed id: 11287639 DOI: 10.1073/pnas.071051098

Date:

12-Mar-01 Release date: 28-Mar-01

Protein chains

P10587  (MYH11_CHICK) -  Myosin-11 from Gallus gallus

Seq: 1979 a.a.

Struc: 909 a.a.*

Protein chains

P02607  (MYL6_CHICK) -  Myosin light polypeptide 6 from Gallus gallus

Seq: 151 a.a.

Struc: 148 a.a.

Protein chains

P02609  (MYL11_CHICK) -  Myosin regulatory light chain 11 from Gallus gallus

Seq: 168 a.a.

Struc: 138 a.a.*

* PDB and UniProt seqs differ at 33 residue positions (black crosses)

Enzyme reactions

• Enzyme class: Chains S, V: E.C.3.6.1.32 - Transferred entry: 5.6.1.8.

DOI no: 10.1073/pnas.071051098

Proc Natl Acad Sci U S A 98:4361-4366 (2001)

PubMed id: 11287639

Three-dimensional image reconstruction of dephosphorylated smooth muscle heavy meromyosin reveals asymmetry in the interaction between myosin heads and placement of subfragment 2.

T.Wendt, D.Taylor, K.M.Trybus, K.Taylor.

ABSTRACT

Regulation of the actin-activated ATPase of smooth muscle myosin II is known to involve an interaction between the two heads that is controlled by phosphorylation of the regulatory light chain. However, the three-dimensional structure of this inactivated form has been unknown. We have used a lipid monolayer to obtain two-dimensional crystalline arrays of the unphosphorylated inactive form of smooth muscle heavy meromyosin suitable for structural studies by electron cryomicroscopy of unstained, frozen-hydrated specimens. The three-dimensional structure reveals an asymmetric interaction between the two myosin heads. The ATPase activity of one head is sterically "blocked" because part of its actin-binding interface is positioned onto the converter domain of the second head. ATPase activity of the second head, which can bind actin, appears to be inhibited through stabilization of converter domain movements needed to release phosphate and achieve strong actin binding. When the subfragment 2 domain of heavy meromyosin is oriented as it would be in an actomyosin filament lattice, the position of the heads is very different from that needed to bind actin, suggesting an additional contribution to ATPase inhibition in situ.

Selected figure(s)

Figure 3.
Fig. 3. Docking of unphosphorylated HMM onto actin. (A) The "free" head of the HMM model is oriented on actin by using the actin-binding domain of rigor skeletal muscle actomyosin (Inset) as the reference. The smooth muscle S1 with a transition state analog at the active site appears with the lever arm up (15) in contrast to the lever arm down-postpowerstroke conformation of skeletal muscle actomyosin (35). The HMM model, when oriented via the actin-binding domain, verifies that one head can interact with actin without steric hindrance from the second head. The orientation of the double-headed myosin in B represents the arrangement with the S2[lll] segment oriented toward the direction of force transmission, as would occur within the muscle lattice. The head orientations in this configuration do not favor actin binding by either head.

Figure 4.
Fig. 4. Diagram illustrating a model for the structural changes that occur on activation of smooth muscle myosin. (A) In the "off" state, the two heads of myosin are in an orientation that is disadvantageous for actin binding by either head. (B) On phosphorylation of the RLC, the head-head interaction is interrupted, and both can search independently for actin monomers suitably placed for binding. (C) Myosin heads bind actin in the prepowerstroke position, which on filament sliding will transform to the rigor-like configuration that characterizes the end of the powerstroke. Note that the initial attachment to actin is likely to be considerably less ordered than implied by the cartoon (36).

Figures were selected by an automated process.