Structural relationships of actin, myosin, and tropomyosin revealed by cryo-electron microscopy.
Open Access
- 30 June 1987
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 105 (1), 29-39
- https://doi.org/10.1083/jcb.105.1.29
Abstract
We have calculated three-dimensional maps from images of myosin subfragment-1 (S1)-decorated thin filaments and S1-decorated actin filaments preserved in frozen solution. By averaging many data sets we obtained highly reproducible maps that can be interpreted simply to provide a model for the native structure of decorated filaments. From our results we have made the following conclusions. The bulk of the actin monomer is .apprx. 65 .times. 40 .times. 40 .ANG. and is composed of two domains. In the filaments the monomers are strongly connected along the genetic helix with weaker connections following the long pitch helix. The long axis of the monomer lies roughly perpendicular to the filament axis. The myosin head (S1) approaches the actin filament tangentially and binds to a single actin, the major interaction being with the outermost domain of actin. In the map the longest chord of S1 is .apprx. 130 .ANG.. The region of S1 closest to actin is of high density, whereas the part furthest away is poorly defined and may be disordered. By comparing maps from decorated thin filaments with those from decorated actin, we demonstrate that tropomyosin is bound to the inner domain of actin just in front of the myosin binding site at a radius of .apprx. 40 .ANG.. A small change in the azimuthal position of tropomyosin, as has been suggested by others to occur during Ca2+-mediated regulation in vertebrate striated muscle, appears to be insufficient to eclipse totally the major site of interaction between actin and myosin.This publication has 41 references indexed in Scilit:
- Binding of myosin subfragment 1 to glycerinated insect flight muscle in the rigor stateBiophysical Journal, 1985
- Three-Dimensional Image Analysis of the Complex of Thin Filaments and Myosin Molecules from Skeletal Muscle. IV.1 Reconstitution from Minimal- and High-Dose Images of the Actin-Tropomyosin-Myosin Subfragment-1 Complex2The Journal of Biochemistry, 1985
- Diffraction patterns from stained and unstained helices: Consistency or contradiction?Ultramicroscopy, 1984
- Molecular structure determination of crystalline specimens in frozen aqueous solutionsUltramicroscopy, 1984
- Crystallization of myosin subfragment 1.Proceedings of the National Academy of Sciences, 1984
- Two configurations of a channel-forming membrane proteinNature, 1984
- A new myosin fragment: visualization of the regulatory domainNature, 1984
- Electron microscopy of scallop myosinJournal of Molecular Biology, 1983
- Crystallographic studies of the chicken gizzard G-actin X DNase I complex at 5A resolution.1983
- Electron microscopy of frozen biological suspensionsJournal of Microscopy, 1983