Download MendeleyStructural Basis of the Substrate Selectivity of Viperin.
Fenwick, M.K., Su, D., Dong, M., Lin, H., Ealick, S.E.(2020) Biochemistry 59: 652-662
- PubMed: 31917549
- DOI: https://doi.org/10.1021/acs.biochem.9b00741
- Primary Citation of Related Structures:
6Q2P, 6Q2Q - PubMed Abstract:
Viperin is a radical S -adenosylmethionine (SAM) enzyme that inhibits viral replication by converting cytidine triphosphate (CTP) into 3'-deoxy-3',4'-didehydro-CTP and by additional undefined mechanisms operating through its N- and C-terminal domains. Here, we describe crystal structures of viperin bound to a SAM analogue and CTP or uridine triphosphate (UTP) and report kinetic parameters for viperin-catalyzed reactions with CTP or UTP as substrates. Viperin orients the C4' hydrogen atom of CTP and UTP similarly for abstraction by a 5'-deoxyadenosyl radical, but the uracil moiety introduces unfavorable interactions that prevent tight binding of UTP. Consistently, k cat is similar for CTP and UTP whereas the K m for UTP is much greater. The structures also show that nucleotide binding results in ordering of the C-terminal tail and reveal that this region contains a P-loop that binds the γ-phosphate of the bound nucleotide. Collectively, the results explain the selectivity for CTP and reveal a structural role for the C-terminal tail in binding CTP and UTP.
