Expression, purification, and functional characterization of a stable helicase domain from a tomato mosaic virus replication protein

► We expressed the ToMV replication proteins that contain the helicase domain. ► We determined the stable helicase fragment. ► Its N-terminal part was necessary for NTPase activity and stability. ► We developed an efficient expression and purification procedures for the fragment. ► The stable fragment has nucleoside 5′-triphosphatase activity.