van Aken D, Benckhuijsen WE, Drijfhout JW, Wassenaar AL, Gorbalenya AE, Snijder EJ. Expression, purification, and in vitro activity of an arterivirus main proteinase.
Virus Res 2006;
120:97-106. [PMID:
16527369 PMCID:
PMC7114227 DOI:
10.1016/j.virusres.2006.01.025]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2005] [Revised: 01/26/2006] [Accepted: 01/30/2006] [Indexed: 11/20/2022]
Abstract
To allow the biochemical and structural characterization of the chymotrypsin-like "main proteinase" (non-structural protein 4; nsp4) of the arterivirus prototype Equine Arteritis Virus (EAV), we developed protocols for the large-scale production of recombinant nsp4 in Escherichia coli. The nsp4 proteinase was expressed either fused to maltose binding protein or carrying a C-terminal hexahistidine tag. Following purification, the nsp4 moiety of MBP-nsp4 was successfully used for structural studies [Barrette-Ng, I.H., Ng, K.K.S., Mark, B.L., van Aken, D., Cherney, M.M., Garen, C, Kolodenko, Y., Gorbalenya, A.E., Snijder, E.J., James, M.N.G, 2002. Structure of arterivirus nsp4-the smallest chymotrypsin-like proteinase with an alpha/beta C-terminal extension and alternate conformations of the oxyanion hole. J. Biol. Chem. 277, 39960-39966]. Furthermore, both forms of the EAV proteinase were shown to be proteolytically active in two different trans-cleavage assays. Recombinant nsp4 cleaved the cognate nsp6/7- and nsp7/8 site in in vitro synthesized substrates. In a synthetic peptide-based activity assay, the potential of the recombinant proteinase to cleave peptides mimicking the P9-P7' residues of six nsp4 cleavage sites was investigated. The peptide representing the EAV nsp7/8 junction was used to optimize the reaction conditions (pH 7.5, 25mM NaCl, 30% glycerol at 30 degrees C), which resulted in a maximum turnover of 15% of this substrate in 4h, using a substrate to enzyme molar ratio of 24:1. The assays described in this study can be used for a more extensive biochemical characterization of the EAV main proteinase, including studies aiming to identify inhibitors of proteolytic activity.
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