4rwn
From Proteopedia
Crystal structure of the pre-reactive state of porcine OAS1
Structural highlights
Function[OAS1_PIG] Interferon-induced, dsRNA-activated antiviral enzyme which plays a critical role in cellular innate antiviral response. In addition, it may also play a role in other cellular processes such as apoptosis, cell growth, differentiation and gene regulation. Synthesizes higher oligomers of 2'-5'-oligoadenylates (2-5A) from ATP which then bind to the inactive monomeric form of ribonuclease L (RNase L) leading to its dimerization and subsequent activation. Activation of RNase L leads to degradation of cellular as well as viral RNA, resulting in the inhibition of protein synthesis, thus terminating viral replication. Can mediate the antiviral effect via the classical RNase L-dependent pathway or an alternative antiviral pathway independent of RNase L. The secreted form displays antiviral effect against vesicular stomatitis virus (VSV), herpes simplex virus type 2 (HSV-2), and encephalomyocarditis virus (EMCV) and stimulates the alternative antiviral pathway independent of RNase L.[1] Publication Abstract from PubMed2'-5'-Oligoadenylate synthetases (OASs) produce the second messenger 2'-5'-oligoadenylate, which activates RNase L to induce an intrinsic antiviral state. We report on the crystal structures of catalytic intermediates of OAS1 including the OAS1.dsRNA complex without substrates, with a donor substrate, and with both donor and acceptor substrates. Combined with kinetic studies of point mutants and the previously published structure of the apo form of OAS1, the new data suggest a sequential mechanism of OAS activation and show the individual roles of each component. They reveal a dsRNA-mediated push-pull effect responsible for large conformational changes in OAS1, the catalytic role of the active site Mg(2+), and the structural basis for the 2'-specificity of product formation. Our data reveal similarities and differences in the activation mechanisms of members of the OAS/cyclic GMP-AMP synthase family of innate immune sensors. In particular, they show how helix 3103-alpha5 blocks the synthesis of cyclic dinucleotides by OAS1. The Activation Mechanism of 2'-5'-Oligoadenylate Synthetase Gives New Insights Into OAS/cGAS Triggers of Innate Immunity.,Lohofener J, Steinke N, Kay-Fedorov P, Baruch P, Nikulin A, Tishchenko S, Manstein DJ, Fedorov R Structure. 2015 May 5;23(5):851-62. doi: 10.1016/j.str.2015.03.012. Epub 2015 Apr, 16. PMID:25892109[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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