The structure of the rigor complex and its implications for the power stroke.

Abstract

Decorated actin provides a model system for studying the strong interaction between actin and myosin. Cryo-energy-filter electron microscopy has recently yielded a 14 A resolution map of rabbit skeletal actin decorated with chicken skeletal S1. The crystal structure of the cross-bridge from skeletal chicken myosin could not be fitted into the three-dimensional electron microscope map without some deformation. However, a newly published structure of the nucleotide-free myosin V cross-bridge, which is apparently already in the strong binding form, can be fitted into the three-dimensional reconstruction without distortion. This supports the notion that nucleotide-free myosin V is an excellent model for strongly bound myosin and allows us to describe the actin-myosin interface. In myosin V the switch 2 element is closed although the lever arm is down (post-power stroke). Therefore, it appears likely that switch 2 does not open very much during the power stroke. The myosin V structure also differs from the chicken skeletal myosin structure in the nucleotide-binding site and the degree of bending of the backbone beta-sheet. These suggest a mechanism for the control of the power stroke by strong actin binding.

• Authors: K C Holmes, R R Schröder, H L Sweeney, Anne Houdusse
• Journal: Philosophical transactions of the Royal Society of London. Series B, Biological sciences (Philos Trans R Soc Lond B Biol Sci) Vol. 359 Issue 1452 Pg. 1819-28 (Dec 29 2004) ISSN: 0962-8436 [Print] England
• PMID: 15647158 (Publication Type: Journal Article, Review)

Chemical References

• Actins
• Myosins

Topics

• Actins (physiology)
• Animals
• Biomechanical Phenomena
• Models, Biological
• Models, Molecular
• Muscle Contraction (physiology)
• Muscle, Skeletal (physiology)
• Myosins (physiology)
• Protein Conformation