| Description | Proteins containing this domain include human OAS1, -2, -3, and OASL. CCA-adding enzymes add the sequence [cytidine(C)-cytidine-adenosine (A)], one nucleotide at a time, onto the 3' end of tRNA, in a template-independent reaction. This class I group includes the archaeal Sulfolobus shibatae and Archeoglobus fulgidus CCA-adding enzymes. It belongs to the Pol beta-like NT superfamily. In the majority of enzymes in this superfamily, two carboxylates, Dx[D/E], together with a third more distal carboxylate, coordinate two divalent metal cations involved in a two-metal ion mechanism of nucleotide addition. These carboxylate residues are conserved in this family [ , , ].In vertebrates, 2-5OASs (2'-5'-oligoadenylate synthetases) are induced by interferon during the innate immune response to protect against RNA virus infections. In the presence of an RNA activator, 2-5OASs catalyze the oligomerization of ATP into 2-5A. 2-5A activates endoribonuclease L, which leads to degradation of the viral RNA. 2-5OASs are also implicated in cell growth control, differentiation, and apoptosis [ ].Three distinct classes of 2-5A synthetases have been described that correspond to proteins of 40-46 Kd, 69-71 Kd, and 100 Kd. The 40 and 46 Kd forms are produced by alternative splicing of the same gene. The 69 and 71 Kd forms are also produced by alternative splicing of a gene and consist of two adjacent homologous domains whose sequences are highly similar to that of the 40/46 Kd forms. The sequence of the 100 Kd form is not yet known. | Name | 2-5OAS/ClassI-CCAase, nucleotidyltransferase domain |
| Short Name | NT_2-5OAS_ClassI-CCAase | Type | Domain |
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