Chikungunya virus (CHIKV) non-structural
protein 2 (nsP2) is a multifunctional
protein that is considered a master regulator of the viral life cycle and a main viral factor responsible for cytopathic effects and subversion of
antiviral defense. The C-terminal part of nsP2 possesses
protease activity, whereas the N-terminal part exhibits
NTPase and
RNA triphosphatase activity and is proposed to have helicase activity. Bioinformatics analysis classified CHIKV nsP2 into helicase superfamily 1. However, the biochemical significance of a coexistence of two functionally unrelated modules in this single
protein remains unknown. In this study, recombinant nsP2 demonstrated unwinding of
double-stranded RNA in a 5'-3' directionally biased manner and
RNA strand annealing activity. Comparative analysis of
NTPase and helicase activities of wild type nsP2 with enzymatic capabilities of different truncated or N-terminally extended variants of nsP2 revealed that the C-terminal part of the
protein is indispensable for helicase functionality and presumably provides a platform for
RNA binding, whereas the N-terminal-most region is apparently involved in obtaining a conformation of nsP2 that allows for its maximal enzymatic activities. The establishment of the protocols for the production of biochemically active CHIKV nsP2 and optimization of the parameters for helicase and
NTPase assays are expected to provide the starting point for a further search of possibilities for therapeutic interventions to suppress alphaviral
infections.