%0 Journal Article %A Thole, Vera %A Hull, Roger %T Characterization of a protein from Rice tungro spherical virus with serine proteinase-like activity %D 2002 %J Journal of General Virology, %V 83 %N 12 %P 3179-3186 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-83-12-3179 %I Microbiology Society, %X The RNA genome of Rice tungro spherical virus (RTSV) is predicted to be expressed as a large polyprotein precursor (Shen et al., Virology 193, 621–630, 1993 ). The polyprotein is processed by at least one virus-encoded protease located adjacent to the C-terminal putative RNA polymerase which shows sequence similarity to viral serine-like proteases. The catalytic activity of this protease was explored using in vitro transcription/translation systems. Besides acting in cis, the protease had activity in trans on precursors containing regions of the 3’ half of the polyprotein but did not process a substrate consisting of a precursor of the coat proteins. The substitution mutation of Asp2735 of the RTSV polyprotein had no effect on proteolysis; however, His2680, Glu2717, Cys2811 and His2830 proved to be essential for catalytic activity and could constitute the catalytic centre and/or substrate-binding pocket of the RTSV 3C-like protease. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-83-12-3179