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Phosphorylation of Subunit Proteins of Intermediate Filaments from Chicken Muscle and Nonmuscle Cells

O'Connor, Clare M. and Balzer, David R., Jr. and Lazarides, Elias (1979) Phosphorylation of Subunit Proteins of Intermediate Filaments from Chicken Muscle and Nonmuscle Cells. Proceedings of the National Academy of Sciences of the United States of America, 76 (2). pp. 819-823. ISSN 0027-8424.

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The phosphorylation of the subunit proteins of intermediate (10-nm) filaments has been investigated in chicken muscle and nonmuscle cells by using a two-dimensional gel electrophoresis system. Desmin, the 50,000-dalton subunit protein of the intermediate filaments of muscle, had previously been shown to exist as two major isoelectric variants--alpha and ß --in smooth, skeletal, and cardiac chicken muscle. Incubation of skeletal and smooth muscle tissue with 32PO4{}3- reveals that the acidic variant, alpha -desmin, and three other desmin variants are phosphorylated in vivo and in vitro. Under the same conditions, minor components of alpha - and ß -tropomyosin from skeletal muscle, but not smooth muscle, are also phosphorylated. Both the phosphorylated desmin variants and the nonphosphorylated ß -desmin variant remain insoluble under conditions that solubilize actin and myosin filaments, but leave Z-discs and intermediate filaments insoluble. Primary cultures of embryonic chicken muscle labeled with 32PO4{}3- possess, in addition to the desmin variants described above, a major nonphosphorylated and multiple phosphorylated variants of the 52,000-dalton, fibroblast-type intermediate filament protein (IFP). Filamentous cytoskeletons, prepared from primary myogenic cultures by Triton X-100 extraction, contain actin and all of the phosphorylated and nonphosphorylated variants of both desmin and the IFP. Similarly, these proteins are the major components of the caps of aggregated 10-nm filaments isolated from the same cell cultures previously exposed to Colcemid. These results demonstrate that a nonphosphorylated and several phosphorylated variants of desmin and IFP are present in assembled structures in muscle and nonmuscle cells.

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Additional Information:Copyright © 1979 by the National Academy of Sciences Communicated by James F. Bonner, November 16, 1978 We thank Ilga Lielausis for her expert technical assistance; Dr. Tom Maniatis for his advice on autoradiography; and B. D. Hubbard, B. L. Granger, and D. L. Gard for their comments on the manuscript. This work was supported by a grant from the National Institutes of Health (PHS GM-06965-18) and by a grant from the Muscular Dystrophy Association of America. C.M.O. was also supported by a National Institutes of Health Postdoctoral Fellowship. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.
Subject Keywords:desmin; tropomyosin; two-dimensional gel electrophoresis
Issue or Number:2
Record Number:CaltechAUTHORS:OCOpnas79
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5775
Deposited By: Archive Administrator
Deposited On:01 Nov 2006
Last Modified:02 Oct 2019 23:26

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