Alternative substrate kinetics of SARS-CoV-2 Nsp15 endonuclease reveals a specificity landscape dominated by RNA structure.

ABSTRACT: Coronavirus endoribonuclease Nsp15 contributes to the evasion of host innate immunity by suppressing levels of viral dsRNA. Nsp15 cleaves both ssRNA and dsRNA in vitro with a strong preference for unpaired or bulged U residues, and its activity is stimulated by divalent ions. Here, we systematically quantified effects of RNA sequence and structure context that define its specificity. The results show that sequence preference for U↓A/G, observed previously, contributes only ca. 2-fold to kcat/Km. In contrast, dsRNA structure flanking a bulged U residue increases kcat/Km by an order of magnitude compared to ssRNA while base pairing in dsRNA essentially blocks cleavage. Despite enormous differences in multiple turnover kinetics, the effect of RNA structure on the cleavage step is minimal. Sur

SUBMITTER: Kalia N 

PROVIDER: S-EPMC11602132 | biostudies-literature | 2024 Nov

REPOSITORIES: biostudies-literature