Amino acid sequence of an anti-tumor protein from Rana pipiens oocytes and early embryos. Homology to pancreatic ribonucleases.

Rana pipiens oocytes and early embryos contain large amounts of a basic protein with antiproliferative/cytotoxic activity against several tumor cell lines in vitro (Darzynkiewicz, Z., Carter, S. P., Mikulski, S. M., Ardelt, W., and Shogen, K. (1988) Cell Tissue Kinet. 21, 169-182; Mikulski, S.M., Viera, A., Ardelt, W., Menduke, H., and Shogen, K. (1990) Cell Tissue Kinet. 23, 237-246), as well as antitumor activity in vivo (Mikulski, S. M., Ardelt, W., Shogen, K., Bernstein, E. H., and Menduke, H. (1990) J. Natl. Cancer Inst. 82, 151-153). The protein, provisionally named P-30 Protein, was purified to homogeneity from early embryos and characterized. It is a single-chain protein consisting of 104 amino acid residues in the following sequence: less than Glu1-Asp-Trp-Leu-Thr-Phe-Gln-Lys-Lys-His-Ile-Thr-Asn-Thr- Arg15-Asp-Val-Asp-Cys-Asp-Ans-Ile-Met-Ser-Thr-Asn-Leu-Phe-His-C ys30-Lys-Asp-Lys - Asn-Thr-Phe-Ile-Tyr-Ser-Arg-Pro-Glu-Pro-Val-Lys45-Ala-Ile-Cys-Lys- Gly-Ile-Ile- Ala-Ser-Lys-Asn-Val-Leu-Thr-Thr60-Ser-Glu-Phe-Tyr-Leu-Ser-Asp -Cys-Asn-Val-Thr-Ser-Arg-Por-Cys75-Lys-Tyr-Lys-Leu-Lys-Lys-Ser-Thr -Asn-Lys-Phe- Cys-Val-Thr-Cys90-Glu-Asn-Gln-Ala-Pro-Val-His-Phe-Val-Gly-Val-Gly- Ser-Cys104-OH . Its molecular weight calculated from the sequence is 11,819. The sequence homology clearly indicates that the protein belongs to the superfamily of pancreatic ribonuclease. It is also demonstrated that it indeed exhibits a ribonucleolytic activity against highly polymerized RNA and that this activity seems to be essential for its antiproliferative/cytotoxic effects.