Human<unk>  is a single polypeptide of 361 amino acids with a predicted molecular weight of 42 kDa. The N-terminal 42 amino acids of<unk>  forms amphipathic alpha-helix, which is relatively less conserved in different species and has a minor effect on the antiviral activity of<unk> . The N-terminal domain of<unk>  is required for its localization to the ER and lipid droplets. Amino acids 77-209 of<unk>  constitute the radical S-adenosyl methionine (SAM) domain, containing four conserved motifs. Motif 1 has three conserved cysteine residues, CxxCxxC, which is the Fe-S binding motif and also essential for antiviral activity. The C-terminal 218-361 amino acids of<unk>  are highly conserved in different species and essential for<unk>  dimerization. The C-terminal tail appears to be critical for the antiviral activities against HCV since a C-terminal flag tagged of<unk>  lost its antiviral activity. When<unk>  is bound to SAM and Cytidine triphosphate (CTP) or uridine triphosphate (UTP) is used as a substrate, different kinetic parameters are achieved. It is predicted that the CTP substrate binds much more tightly with<unk>  because of the low Km value of the substrate. However, the overall structure of both UTP- and CTP-bound compounds are similar. The difference being that the uracil moiety is less effective then the cytosine moiety at binding and ordering turns A and B. Nucleotide-free<unk>  contains a (βα)6 partial barrel and has a disordered N-terminal extension and a partially ordered C-terminal extension. When the C-terminal tail is ordered, a six-residue α-helix, an eight-residue P-loop (that binds the γ-phosphate of CTP), and a 310-helix are revealed.
Viperin
Latrotoxin
Alpha-neurotoxin
Bukatoxin
Bungarotoxin
Tetrahydrocannabinol
Brevetoxin
Neurotoxin