UPF1 (or regulator of nonsense transcripts 1 homologue) is an essential RNA helicase that detects mRNAs containing premature stop codons and triggers their degradation. Together with UPF2 and UPF3, forms a surveillance complex, in which UPF2 acts as a bridge between UPF1 and UPF3. UPF2 and UPF3 are non-enzymatic components of the complex that stimulate the activity of UPF1 [1, 2]. UPF1 has a N-terminal cysteine/histidine-rich zinc-binding domain (CH/ZBD), a regulatory 1B domain, followed by a helicase core that belongs to superfamily 1 (SF1). This entry represents 1B domain of UPF1 which has a regulatory role. It suffers conformational changes from an inhibitory state to a transition-state complex that modulate RNA binding [1, 2].

1: Unusual bipartite mode of interaction between the nonsense-mediated decay factors, UPF1 and UPF2. Clerici M, Mourao A, Gutsche I, Gehring NH, Hentze MW, Kulozik A, Kadlec J, Sattler M, Cusack S; EMBO J. 2009;28:2293-2306. PMID:19556969

2: Molecular mechanisms for the RNA-dependent ATPase activity of Upf1 and its regulation by Upf2. Chakrabarti S, Jayachandran U, Bonneau F, Fiorini F, Basquin C, Domcke S, Le Hir H, Conti E; Mol Cell. 2011;41:693-703. PMID:21419344