Abstract
Natural actomyosin at µ = 0.6 appears in various forms, including the regular arrowhead structures originally reported by Huxley (1), when it has been stained negatively with 1% uranyl acetate. In addition to the arrowheads, thin whiskers, 700–1200 A in length and 20 A in width, attached to the arm of the arrowheads have been demonstrated. The dimensions of the whiskers and arms of the arrowheads are practically the same as those of the light meromyosin (LMM) and the heavy meromyosin (HMM) moieties of the single myosin molecule, respectively. Changes in the electron microscopically distinguishable elements during aggregation of natural actomyosin on reduction of the ionic strength have been observed. At µ = 0.4, partial aggregation of the LMM whiskers begins to result in some parallel alignment of the arrowhead-bearing filaments (acto-HMM). In the range of µ = 0.3–0.1, the LMM whiskers merge into smooth filaments which are arranged alternatingly with arrowhead-bearing filaments. Thus, lateral aggregation of composite actomyosin filaments (acto-HMM + LMM whiskers) results with the LMM moieties as links. This view is supported by the following facts: (a) acto-HMM is devoid of whiskers and does not show lateral aggregation at µ = 0.1; (b) natural actomyosin digested with trypsin at µ = 0.6, which was followed by removal of LMM aggregates at low ionic strength, is essentially the same as acto-HMM at µ = 0.1; and (c) digestion with trypsin of natural actomyosin at µ = 0.2 for varying periods of time leads to a separation of arrowhead-bearing filaments from LMM aggregates.
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Selected References
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- Carney J. A., Brown A. L., Jr An electron microscope study of canine cardiac myosin and some of its aggregates. J Cell Biol. 1966 Feb;28(2):375–389. doi: 10.1083/jcb.28.2.375. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DEPUE R. H., Jr, RICE R. V. F-ACTIN IS A RIGHT-HANDED HELIX. J Mol Biol. 1965 May;12:302–303. doi: 10.1016/s0022-2836(65)80306-0. [DOI] [PubMed] [Google Scholar]
- EBASHI S., EBASHI F. A NEW PROTEIN COMPONENT PARTICIPATING IN THE SUPERPRECIPITATION OF MYOSIN B. J Biochem. 1964 Jun;55:604–613. doi: 10.1093/oxfordjournals.jbchem.a127933. [DOI] [PubMed] [Google Scholar]
- LOWEY S. MYOSIN SUBSTRUCTURE: ISOLATION OF A HELICAL SUBUNIT FROM HEAVY MEROMYOSIN. Science. 1964 Aug 7;145(3632):597–599. doi: 10.1126/science.145.3632.597. [DOI] [PubMed] [Google Scholar]
- MARUYAMA K., GERGELY J. Interaction of actomyosin with adenosine triphosphate at low ionic strength. I. Dis-sociation of actomyosin during the clear phase. J Biol Chem. 1962 Apr;237:1095–1099. [PubMed] [Google Scholar]
- RICE R. V. Conformation of individual macromolecular particles from myosin solution. Biochim Biophys Acta. 1961 Sep 30;52:602–604. doi: 10.1016/0006-3002(61)90427-9. [DOI] [PubMed] [Google Scholar]
- Slayter H. S., Lowey S. Substructure of the myosin molecule as visualized by electron microscopy. Proc Natl Acad Sci U S A. 1967 Oct;58(4):1611–1618. doi: 10.1073/pnas.58.4.1611. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Young M. Studies on the structural basis of the interaction of myosin and actin. Proc Natl Acad Sci U S A. 1967 Dec;58(6):2393–2400. doi: 10.1073/pnas.58.6.2393. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ZOBEL C. R., CARLSON F. D. An electron microscopic investigation of myosin and some of its aggregates. J Mol Biol. 1963 Jul;7:78–89. doi: 10.1016/s0022-2836(63)80020-0. [DOI] [PubMed] [Google Scholar]
- Zobel C. R. An electron-microscopic investigation of heavy meromyosin. Biochim Biophys Acta. 1967 Jun 27;140(2):222–230. doi: 10.1016/0005-2795(67)90462-x. [DOI] [PubMed] [Google Scholar]