title: Chikungunya nsP2 protease is not a papain-like cysteine protease and the catalytic dyad cysteine is interchangeable with a proximal serine.
abstract: Chikungunya virus is the pathogenic alphavirus that causes chikungunya fever in humans. In the last decade millions of cases have been reported around the world from Africa to Asia to the Americas. The alphavirus nsP2 protein is multifunctional and is considered to be pivotal to viral replication, as the nsP2 protease activity is critical for proteolytic processing of the viral polyprotein during replication. Classically the alphavirus nsP2 protease is thought to be papain-like with the enzyme reaction proceeding through a cysteine/histidine catalytic dyad. We performed structure-function studies on the chikungunya nsP2 protease and show that the enzyme is not papain-like. Characterization of the catalytic dyad cysteine residue enabled us to identify a nearby serine that is catalytically interchangeable with the dyad cysteine residue. The enzyme retains activity upon alanine replacement of either residue but a replacement of both cysteine and serine residues results in no detectable activity. Protein dynamics appears to allow the use of either the cysteine or the serine residue in catalysis. This switchable dyad residue has not been previously reported for alphavirus nsP2 proteases and would have a major impact on the nsP2 protease as an anti-viral target.
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Thailand.
authors.forename: Chonticha
authors.initials: C
authors.lastname: Saisawang
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Thailand.
authors.forename: Sawanan
authors.initials: S
authors.lastname: Saitornuang
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Thailand.
authors.forename: Pornpan
authors.initials: P
authors.lastname: Sillapee
authors.affiliation: Department of Microbiology, Faculty of Science, Mahidol University, Bangkok, Thailand.|Center for Emerging and Neglected Infectious Diseases, Mahidol University, Thailand.
authors.forename: Sukathida
authors.initials: S
authors.lastname: Ubol
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Thailand.|Center for Emerging and Neglected Infectious Diseases, Mahidol University, Thailand.
authors.forename: Duncan R
authors.initials: DR
authors.lastname: Smith
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Thailand.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Ketterman
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002646:Chikungunya virus / Q000201:enzymology*; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D004795:Enzyme Stability; D007700:Kinetics; D008958:Models, Molecular; D010206:Papain / Q000737:chemistry; D059748:Proteolysis; D012694:Serine / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry*
chemical_list: D014764:Viral Proteins; D012694:Serine; D003546:Cysteine Endopeptidases; C078306:nsP2 proteinase; D010206:Papain