Skip to main content
Biophysical Journal logoLink to Biophysical Journal
. 1995 Apr;68(4 Suppl):298S–305S.

Single-molecule mechanics of heavy meromyosin and S1 interacting with rabbit or Drosophila actins using optical tweezers.

J E Molloy 1, J E Burns 1, J C Sparrow 1, R T Tregear 1, J Kendrick-Jones 1, D C White 1
PMCID: PMC1281954  PMID: 7787095

Abstract

Single-molecule mechanical interactions between rabbit heavy meromyosin (HMM) or subfragment 1 (S1) and rabbit actin were measured with an optical tweezers piconewton, nanometer transducer. Similar intermittent interactions were observed with HMM and S1. The mean magnitude of the single interaction isotonic displacements was 20 nm for HMM and 15 nm with S1. The mean value of the force of single-molecule interactions was 1.8 pN for HMM and 1.7 pN with S1. The stiffness of myosin S1 was determined by applying a sinusoidal length change to the thin filament and measuring the corresponding force; the mean stiffness was 0.13 pN nm-1. By moving an actin filament over a long distance past an isolated S1 head, we found that cross-bridge attachment occurred preferentially at a periodicity of about 40 nm, similar to that of the actin helical repeat. Rate constants for the probability of detachment of HMM from actin were determined from histograms of the lifetime of the attached state. This gave a value of 8 s-1 or 0.8 x 10(6) M-1 s-1 for binding of ATP to the rigor complex. We conclude (1) that our HMM-actin interactions involve just one head, (2) that compliance of the cross-bridge is not in myosin subfragment 2, although we cannot say to what extent contributions arise from myosin S1 or actin, and (3) that the elemental movement can be caused by a change of shape of the S1 head, but that this would have to be much greater than the movements suggested from structural studies of S1 (Rayment et al., 1993).

Full text

PDF
298s

Images in this article

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Drummond D. R., Peckham M., Sparrow J. C., White D. C. Alteration in crossbridge kinetics caused by mutations in actin. Nature. 1990 Nov 29;348(6300):440–442. doi: 10.1038/348440a0. [DOI] [PubMed] [Google Scholar]
  2. Finer J. T., Simmons R. M., Spudich J. A. Single myosin molecule mechanics: piconewton forces and nanometre steps. Nature. 1994 Mar 10;368(6467):113–119. doi: 10.1038/368113a0. [DOI] [PubMed] [Google Scholar]
  3. Huxley A. F., Simmons R. M. Proposed mechanism of force generation in striated muscle. Nature. 1971 Oct 22;233(5321):533–538. doi: 10.1038/233533a0. [DOI] [PubMed] [Google Scholar]
  4. Kron S. J., Toyoshima Y. Y., Uyeda T. Q., Spudich J. A. Assays for actin sliding movement over myosin-coated surfaces. Methods Enzymol. 1991;196:399–416. doi: 10.1016/0076-6879(91)96035-p. [DOI] [PubMed] [Google Scholar]
  5. Margossian S. S., Lowey S. Preparation of myosin and its subfragments from rabbit skeletal muscle. Methods Enzymol. 1982;85(Pt B):55–71. doi: 10.1016/0076-6879(82)85009-x. [DOI] [PubMed] [Google Scholar]
  6. Pardee J. D., Spudich J. A. Purification of muscle actin. Methods Cell Biol. 1982;24:271–289. doi: 10.1016/s0091-679x(08)60661-5. [DOI] [PubMed] [Google Scholar]
  7. Rayment I., Holden H. M., Whittaker M., Yohn C. B., Lorenz M., Holmes K. C., Milligan R. A. Structure of the actin-myosin complex and its implications for muscle contraction. Science. 1993 Jul 2;261(5117):58–65. doi: 10.1126/science.8316858. [DOI] [PubMed] [Google Scholar]
  8. Reedy M. K. Ultrastructure of insect flight muscle. I. Screw sense and structural grouping in the rigor cross-bridge lattice. J Mol Biol. 1968 Jan 28;31(2):155–176. doi: 10.1016/0022-2836(68)90437-3. [DOI] [PubMed] [Google Scholar]
  9. Svoboda K., Block S. M. Biological applications of optical forces. Annu Rev Biophys Biomol Struct. 1994;23:247–285. doi: 10.1146/annurev.bb.23.060194.001335. [DOI] [PubMed] [Google Scholar]
  10. Svoboda K., Schmidt C. F., Schnapp B. J., Block S. M. Direct observation of kinesin stepping by optical trapping interferometry. Nature. 1993 Oct 21;365(6448):721–727. doi: 10.1038/365721a0. [DOI] [PubMed] [Google Scholar]

Articles from Biophysical Journal are provided here courtesy of The Biophysical Society

RESOURCES