Binding of the Methyl Donor -Adenosyl-l-Methionine to Middle East Respiratory Syndrome Coronavirus 2'--Methyltransferase nsp16 Promotes Recruitment of the Allosteric Activator nsp10.

The Middle East respiratory syndrome coronavirus (MERS-CoV) nonstructural protein 16 (nsp16) is an -adenosyl-l-methionine (SAM)-dependent 2'--methyltransferase (2'-O-MTase) that is thought to methylate the ribose 2'-OH of the first transcribed nucleotide (N) of viral RNA cap structures. This 2'-O-MTase activity is regulated by nsp10. The 2'- methylation prevents virus detection by cell innate immunity mechanisms and viral translation inhibition by the interferon-stimulated IFIT-1 protein.

mRNA Capping by Venezuelan Equine Encephalitis Virus nsP1: Functional Characterization and Implications for Antiviral Research.

Unlabelled: Alphaviruses are known to possess a unique viral mRNA capping mechanism involving the viral nonstructural protein nsP1. This enzyme harbors methyltransferase (MTase) and nsP1 guanylylation (GT) activities catalyzing the transfer of the methyl group from S-adenosylmethionine (AdoMet) to the N7 position of a GTP molecule followed by the formation of an m(7)GMP-nsP1 adduct. Subsequent transfer of m(7)GMP onto the 5' end of the viral mRNA has not been demonstrated in vitro yet.