Characterization of the cysteine protease domain of Semliki Forest virus replicase protein nsP2 by in vitro mutagenesis.
The function of Semliki Forest Virus nsP2 protease was investigated by site-directed mutagenesis. Mutations were introduced in its protease domain, Pro39, and the mutated proteins were expressed in Escherichia coli, purified and their activity in vitro was compared to that of the wild type Pro39. Mutations M781T, A662T and G577R, found in temperature-sensitive virus strains, rendered the enzyme temperature-sensitive in vitro as well. Five conserved residues were required for the proteolytic activity of Pro39. Changes affecting Cys478, His548, and Trp549 resulted in complete inactivation of the enzyme, whereas the replacements N600D and N605D significantly impaired its activity. The importance of Trp549 for the proteolytic cleavage specificity is discussed and a new structural motif involved in substrate recognition by cysteine proteases is proposed.
Golubtsov
Andrey
A
Institute of Biotechnology, Biocenter Viikki, P.O. Box 56, 00014 University of Helsinki, Finland.
Kääriäinen
Leevi
L
Caldentey
Javier
J
D019943:Amino Acid Substitution; D017124:Conserved Sequence; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D012672:Semliki forest virus / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity; D013696:Temperature; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D014764:Viral Proteins; D003546:Cysteine Endopeptidases; C078306:nsP2 proteinase