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Isolation and Characterization of a Cytosol Protein (64/7.2) Present in Large Amounts in Rapidly Growing Hepatomas¹

Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030 [K. S. R., A. C., F. W. H., B. C. W., K. N. N., H. B.], and Department of Biochemistry, Howard University College of Medicine, Washington, D. C. 20059, [H. P. M.]

Protein 64/7.2 (molecular weight/isoelectric point) is present in the cytosol of several hepatomas including the Novikoff hepatoma and Morris hepatomas 9618A, 7794A, and 3924A, but it is not present in liver or 18-hr regenerating liver. Quantitatively, its concentration was highest in Novikoff hepatoma (150 µg/g tissue) and Morris hepatoma 3924A (550 µg/g tissue), which are rapid-growing tumors, less in Morris hepatoma 7794A (72 µg/g tissue), which is of intermediate growth rate, and least in the slow-growing Morris hepatoma 9618A (25 µg/g tissue). Protein 64/7.2 was isolated from Novikoff hepatoma ascites cells in high purity as shown by its migration as a single band on one-dimensional acid-urea-polyacrylamide gels and a single spot on two-dimensional isoelectric focusing sodium dodecyl sulfate-polyacrylamide gels. Its amino acid composition has an acidic to basic amino acid ratio of 1.6. Its amino-terminal amino acid is lysine, and its carboxylterminal amino acid is glycine. Interestingly, the amino acid composition is strikingly similar to that of the phosphorylated Novikoff hepatomas chromatin Protein Cg', partially characterized in our laboratory.

¹ These studies were supported by Cancer Research Center Grant CA-10693, awarded by the National Cancer Institute, Department of Health, Education, and Welfare, by the Pauline Sterne Wolff Memorial Foundation, a generous gift from Mrs. Jack Hutchins, and the Bristol-Myers Fund.

Received 10/31/77. Accepted 4/ 3/78.