nsp10s

Nsp10s refers to the non-structural protein 10 homologs found in nidoviruses, most prominently in coronaviruses. These small, highly conserved proteins serve as essential cofactors within the viral replication-transcription complex and are encoded within the large polyproteins that are processed to form the mature non-structural proteins.

The primary role of nsp10 is to stimulate the activities of other enzymatic components involved in RNA processing. In coronaviruses, nsp10 enhances the exoribonuclease activity of nsp14, which contributes to RNA proofreading, and it also boosts the 2'-O-methyltransferase activity of nsp16, which is involved in the proper capping of viral mRNA. Through these interactions, nsp10s support replication fidelity and help shield viral RNA from host innate immune sensors by promoting proper RNA capping.

Structurally, nsp10s are small proteins, typically around 120 to 140 amino acids in coronaviruses, and they contain metal-binding motifs that coordinate zinc ions, contributing to a stable fold. They function by forming complexes with nsp14 or nsp16, rather than exerting independent enzymatic activity. The nsp10–nsp14 and nsp10–nsp16 complexes have been characterized in several coronaviruses, including SARS-CoV-2, SARS-CoV, and MERS-CoV, with structural studies revealing the molecular basis of cofactor interactions.

Across nidoviruses, nsp10s show considerable sequence conservation but vary among species. Because of their central coordinating role in RNA processing and capping, nsp10s are considered potential targets for antiviral strategies aimed at disrupting nsp10–nsp14 or nsp10–nsp16 interactions to impair viral replication.