Chakard Chalayut. Cloning expression purification and enzymological characterization of NS2BNS3 protease protein of japanese encephalitis virus. Master's Degree(Molecular Genetics and Genetic Engineering). Mahidol University. Mahidol University Library and Knowledge Center. : Mahidol University, 2009.
Cloning expression purification and enzymological characterization of NS2BNS3 protease protein of japanese encephalitis virus
Abstract:
Japanese Encephalitis Virus (JEV), a member of the Flaviviridae family, is a
mosquito borne neurotropic flavivirus that causes severe diseases of the central nervous
system. Currently, several vaccines are in clinical use, however, their use is restricted due to
high costs and occasional adverse effects. The development of small molecule drugs against
viral target enzymes such as the NS2B-NS3 protease therefore are urgently required. This
study therefore aimed to analyze the differences in the mechanism of cofactor activation
between dengue virus and Japanese encephalitis virus NS2B(H)-NS3(pro) by characterization
of the two-component protease by establishing a rapid, sensitive and easy to perform assay
with the fluorogenic substrates. In this study, the peptide substrates incorporated with
fluorogenic group (amc) were used and a general methodology for the cloning, expression and
purification of the Japanese encephalitis virus protease was developed. The sequence of
NS2B-NS3 from JEV was obtained by synthetic gene. The protease complex NS2B(H)-
NS3pro was obtained by SOE-PCR. Constructs were cloned and over expressed in E.coli,
purified by metal affinity chromatography and size exclusion, then the protein sample was
subjected to analysis by SDS-PAGE, Western Blotting and a fluorogenic assay with the
synthetic substrate RTKR-amc and GRR-amc. Kinetic studies revealed the kinetic parameters
(Km, kcat) and also demonstrated kinetic differences between dengue and Japanese encephalitis
virus. However, the Japanese Encephalitis virus protease is similar in pH and ionic strength to
the Dengue virus. These novel findings make for a better understanding of the NS2B(H)-
NS3(pro) of Japanese encephalitis virus to the related Flavivirus and provide a starting point
for further characterization of substrate specificity and inhibitor design for the JEV protease.