Two arginine-specific ADP-ribosyltransferase cDNAs (designated AT1 and AT2) were cloned from chicken bone marrow cells. Each cDNA encodes a different peptide of 312 amino acid residues. Homology of deduced amino acid sequences between AT1 and AT2 was 78.3%. We found all six combined peptide sequences of 222 amino acid residues derived from purified chicken heterophil ADP-ribosyltransferase (Mishima, K., Terashima, M., Obara, S., Yamada, K., Imai, K., and Shimoyama, M. (1991) J. Biochem. (Tokyo) 110, 388-394) in the deduced amino acid sequence of AT1, with two amino acid mismatches. Arginine-specific ADP-ribosyltransferase activity was detected in culture medium of COS 7 cells transiently transfected with AT1 cDNA, while activity from the cells transfected with AT2 cDNA was found in both culture medium and cell lysate. AT1 transferase required 2-mercaptoethanol for the activity. The activity was inhibited in the presence of NaCl while AT2 enzyme was activated by either agent. On zymographic in situ gel analysis, estimated molecular masses of the AT1, AT2 and purified chicken heterophil transferases were 32, 34, and 27.5 kDa, respectively. Northern blot analysis with specific probes to AT1 or AT2 cDNAs revealed about a 1.5-kilobase message in chicken bone marrow cells but no signals were observed in heterophils, spleen, and liver of chicken or human HL-60 cells. Highly conserved regions were observed among the deduced amino acid sequences of AT1, AT2, rabbit skeletal muscle transferase, and rodent T-cell surface antigen RT6s.
ADP Ribose Transferases Animals