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Published December 1, 1974 | public
Journal Article Open

Actin is the naturally occurring inhibitor of deoxyribonuclease I

Abstract

Various tissues and cells in culture contain a specific inhibitor of DNase I (EC 3.1.4.5). In this paper evidence is presented that this inhibitor is actin, one of the major structural proteins of muscle and nonmuscle cells. (a) The inhibitor is a major cellular component constituting 5-10% of the soluble protein. (b) It migrates with actin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, having a characteristic molecular weight of 42,000. (c) It has an amino-acid composition closely similar to that of actin. (d) The peptide maps of the two proteins are nearly identical. (e) Skeletal muscle actin inhibits the enzymatic activity of DNase I. (f) DNase I-agarose affinity chromatography quantitatively retains purified skeletal muscle actin, and actin, specifically, from high-speed supernatants of whole cell extracts. (g) An antibody to purified inhibitor protein from calf thymus, used in indirect immunofluorescence on cells grown in culture, stains a two-dimensional network of fibers similar to that seen with an actin-specific antibody. The observation that actin can be isolated by DNase-agarose affinity chromatography provides a useful tool for the biochemical study of actin under different physiological conditions.

Additional Information

© 1974 by the National Academy of Sciences. Communicated by Barbara McClintock, August 29, 1974. We thank Drs. R.F. Gesteland and J.D. Watson for their encouragement and support throughout this work, and Drs. R. Pollack and K. Weber for the generous use of their laboratory facilities. We also thank Drs. R. Goldman and M. Howe for their advice and help in various aspects of this work. This investigation was supported by the National Institutes of Health (Research Grant CA-13106 from the National Cancer Institute).

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August 22, 2023
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