Function of ubiquitin-like domain of chicken 2'-5'-oligoadenylate synthetase in conformational stability.
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.
Tatsumi
Rie
R
Department of Biotechnology, Kyoto Institute of Technology, Kyoto 606-8585, Japan. tatsumi@bio.kit.ac.jp
Sekiya
Sadanori
S
Nakanishi
Ryoko
R
Mizutani
Makoto
M
Kojima
Shin-Ichi
S
Sokawa
Yoshihiro
Y
D015088:2',5'-Oligoadenylate Synthetase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D004795:Enzyme Stability; D004912:Erythrocytes / Q000201:enzymology; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014452:Ubiquitins / Q000737:chemistry*
D014452:Ubiquitins; D015088:2',5'-Oligoadenylate Synthetase