NS3 is a nonstructural multifunctional protein found in pestiviruses that contains an N-terminal protease and a C-terminal helicase. The N-terminal domain is a chymotrypsin-like serine protease, which is responsible for most of the maturation cleavages of the polyprotein precursor in the cytosolic side of the endoplasmic reticulum membrane. The C-terminal domain, about two-thirds of NS3, is a helicase belonging to superfamily 2 (SF2) thought to be important for unwinding highly structured regions of the RNA genome during replication. NS3 plays an essential role in viral polyprotein processing and genome replication. NS3 is a member of the DEAD-like helicase superfamily, a diverse family of proteins involved in ATP-dependent RNA or DNA unwinding. This domain contains the ATP-binding region.
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