Structural and mechanistic studies on the HeLa and chicken liver proteins that catalyze glycinamide ribonucleotide synthesis and formylation and aminoimidazole ribonucleotide synthesis.

Glycinamide ribonucleotide (GAR) transformylase from HeLa cells has been purified 200-fold to apparent homogeneity with a procedure using two affinity resins. The activities glycinamide ribonucleotide synthetase and aminoimidazole ribonucleotide synthetase were found to copurify with GAR transformylase. Glycinamide ribonucleotide synthetase and GAR transformylase were separable only after exposure to chymotrypsin. Antibodies raised to pure L1210 cell GAR transformylase were able to precipitate the glycinamide ribonucleotide transformylase and GAR synthetase activities from HeLa and L1210 cells both in their native and in their proteolytically shortened forms. The compound N-10-(bromoacetyl)-5,8-dideazafolate was found to inhibit formylation but to leave the ATP-requiring synthetase activities intact.