Function of ubiquitin-like domain of chicken 2'-5'-oligoadenylate synthetase in conformational stability

• Published in: Journal of interferon & cytokine research Vol. 23; no. 11; pp. 667 - 676
• Main Authors: Tatsumi, Rie, Sekiya, Sadanori, Nakanishi, Ryoko, Mizutani, Makoto, Kojima, Shin-Ichi, Sokawa, Yoshihiro
• Format: Journal Article
• Language: English
• Published: United States Mary Ann Liebert, Inc 01.11.2003
• Subjects: 2',5'-Oligoadenylate Synthetase - chemistry; 2',5'-Oligoadenylate Synthetase - genetics; 2',5'-Oligoadenylate Synthetase - metabolism; Alleles; Amino Acid Sequence; Animals; Chickens; Enzyme Stability; Erythrocytes - enzymology; Molecular Sequence Data; Mutation; Protein Conformation; Protein Structure, Tertiary; Ubiquitins - chemistry
• ISSN: 1079-9907; 1557-7465
• DOI: 10.1089/107999003322558809

2'-5'-Oligoadenylate synthetase (OAS), an interferon (IFN) induced enzyme, synthesizes 2'-5'-oligoadenylate (2-5A) from ATP when activated by dsRNA. Chicken OAS (ChOAS) has a ubiquitin-like (UbL) domain of two consecutive sequences (UbL1 and UbL2) at its carboxyl-terminus. The OAS gene has at least two alleles, OAS*A and OAS*B. OAS-A is the wild-type (wt) and OAS-B is a mutant deleted of a highly hydrophobic region of UbL1. To study the function of the UbL domain, enzymatic and physiologic properties were compared between OAS-A and OAS-B. OAS-B was more susceptible to trypsin than OAS-A and was converted very quickly into p38, deleting a greater part of the UbL domain. The p38 has the enzymatic activity to synthesize 2-5A. Thermal inactivation of OAS-B occurred at a lower temperature than that of OAS-A and p38, with loss of the ability to bind dsRNA. In contrast to OAS-A, the content of OAS-B in erythrocytes decreased during growth to a very low level. However, red blood cells (RBC) from anemic B/B chickens synthesized OAS-B at a high level comparable to A/A, although OAS-B levels decreased sharply again during maturation to erythrocytes. Thus, OAS-B carrying the mutated UbL domain is unstable compared with OAS-A in vitro and in vivo, and the wt UbL domain may contribute to the stability of the protein structure of ChOAS.