2'-5'-oligoadenylate synthase

{{Infobox protein family

| Symbol = OAS1_C

| Name = 2'-5'-oligoadenylate synthetase

| image =Pig 2'-5'-oligoadenylate synthase PDB=1px5.png

| width =

| caption =Pig 2'-5'-oligoadenylate synthetase, N- and C-terminal domains coloured red and blue, respectively. {{PDB|1PX5}}

| Pfam = PF10421

| Pfam_clan =

| InterPro = IPR018952

| SMART =

| PROSITE =

| MEROPS =

| SCOP =

| TCDB =

| OPM family =

| OPM protein =

| CAZy =

| CDD =

}}

In molecular biology, 2'-5'-oligoadenylate synthetase (2-5A synthetase) is an enzyme ({{EC number|2.7.7.84}}) that reacts to interferon signal. It is an antiviral enzyme that counteracts viral attack by degrading RNAs, both viral and host. The enzyme uses ATP in 2'-specific nucleotidyl transfer reactions to synthesize 2'-5'-oligoadenylates, which activate latent ribonuclease (RNase-L), resulting in degradation of viral RNA and inhibition of virus replication.{{cite journal |vauthors=Ghosh SK, Kusari J, Bandyopadhyay SK, Samanta H, Kumar R, Sen GC | title = Cloning, sequencing, and expression of two murine 2'-5'-oligoadenylate synthetases. Structure-function relationships | journal = J. Biol. Chem. | volume = 266 | issue = 23 | pages = 15293–9 |date=August 1991 | pmid = 1651324 }}

The C-terminal half of 2'-5'-oligoadenylate synthetase, also referred to as domain 2 of the enzyme, is largely alpha-helical and homologous to a tandem ubiquitin repeat. It carries the region of enzymatic activity between{{clarify|date=April 2021}} at the extreme C-terminal end.{{cite journal |vauthors=Hartmann R, Justesen J, Sarkar SN, Sen GC, Yee VC | title = Crystal structure of the 2'-specific and double-stranded RNA-activated interferon-induced antiviral protein 2'-5'-oligoadenylate synthetase | journal = Mol. Cell | volume = 12 | issue = 5 | pages = 1173–85 |date=November 2003 | pmid = 14636576 | doi = 10.1016/S1097-2765(03)00433-7| doi-access = free }}