Identification of the Specific Labile Sites in the 180 kDa Catalytic Polypeptide of the Drosophila melanogaster DNA Polymerase a-Primase Complex

• Published in: Journal of biochemistry (Tokyo) 1993-02, Vol.113 (2), p.126-128
• Main Authors: Kuroda, Kazufumi, Kagiyama-Takahashi, Ritsuko, Okuda, Asuko, Omori, Akira
• Format: Article
• Language: English
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/oxfordjournals.jbchem.a124013

The immunoaffinity-purified DNA polymerase a-primase complex from Drosophila melanogaster Kc cells contains three high molecular weight polypeptides besides the 180 kDa catalytic polypeptide. These polypeptides are immunologically cross-reactive with the 180 kDa polypeptide. When the inununoaffinity-purified complex was kept at 4°C for about four weeks, the amounts of the three polypeptides increased, while the 180 kDa polypeptide completely disappeared. Sodium bisulfite inhibited the decrease in the 180 kDa polypeptide. The N-terminal amino acid sequences of all the polypeptides were all assigned to ones present in a portion close to the N-terminus of the 180 kDa polypeptide. The N-terminal residue of all the three polypeptides was Ser. The cleavage sites were Phel30-Serl31, Thrl80-Serl81, and Phe237-Ser238. These results show that the three polypeptides are cleavage products of the 180 kDa catalytic polypeptide, the cleavage occurring at specific labile sites including a Ser residue. The amino acid residues at the sites are quite different from those (Lys-Lys) in the human 180 kDa catalytic polypeptide.