1B domain of eukaryotic UPF1 helicase, nidovirus SF1 helicases including coronavirus Nsp13 and arterivirus Nsp10, and related proteins
Helicases catalyze NTP-dependent unwinding of nucleic acid duplexes into single strands and are classified based on the arrangement of conserved motifs into six superfamilies. Members of this family belong to helicase superfamily 1 (SF1) and include nidoviral helicases such as Severe Acute Respiratory Syndrome coronavirus (SARS) non-structural protein 13 (SARS-Nsp13), Equine arteritis virus (EAV) Nsp10, and eukaryotic UPF1 RNA helicase. SARS-Nsp13 is a component of the viral RNA synthesis replication and transcription complex (RTC). UPF1 participates in nonsense-mediated mRNA decay (NMD), a pathway which degrades transcripts with premature termination codons. UPF1, EAV Nsp10 and SARS-Nsp13 are multidomain proteins with an N-terminal Cys/His rich zinc-binding domain (CH/ZBD), a 1B domain and a SF1 helicase core. The 1B domain is involved in nucleic acid substrate binding; the 1B domain of EAV Nsp10 undergoes large conformational change upon substrate binding, and together with the 1A and 2A domains of the helicase core form a channel that accommodates the single stranded nucleic acids.
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