Tag Archives: katG
Immunogenicity assay of KatG protein from Mycobacterium tuberculosis in mice: preliminary screening of TB vaccine
P. Purkan1, R. Budiyanto1, R. Akbar1, S. P. A. Wahyuningsih2, W. Retnowati3
1Biochemistry Division, Chemistry Department, Faculty of Sciences and Technology, Airlangga University, Campus C, Jl. Mulyorejo-Surabaya, Indonesia;
2Biology Department, Faculty of Sciences and Technology, Airlangga University, Campus C, Jl. Mulyorejo-Surabaya, Indonesia;
3Microbiology Department, Faculty of Medicine, Airlangga University, Campus C, Jl. Moestopo-Surabaya, Indonesia;
e-mail: purkan@fst.unair.ac.id
The tuberculosis (TB) disease is still widely found even though BCG vaccine given to many people. Ineffectiveness of the BCG vaccine is one of causes that make the difficulties in preventing TB transmission. Objective of the research was to determine the immunogenicity of KatG protein of M. tuberculosis clinical isolate L19 in mice. The KatG protein as antigen was prepared by expression of the katG gene of M. tuberculosis clinical isolate L19 in Escherichia coli BL21 using pColdII-DNA vector. After purification by affinity chromatography, the KatG was vaccinated to mice to detect its immunogenicity. The expression of katG in E. coli BL21 could result in KatG protein with molecular weight 80 kDa in sodium dodecyl sulfate gel electrophoresis (SDS-PAGE). The pure KatG protein could significantly stimulate the immune response of mice by triggering the antibodies production of IgG1, IgG2a, IgG2b, IgG2c, IgG3, and IgM. The highest antibody level was obtained when the mice were vaccinated by KatG L19 with the dose of 45 μg/ml. Of the antibodies, the IgG2c isotype was dominantly produced in the blood serum. The KatG protein exhibited a high immunogenicity in mice, so it is possible to develop as a vaccine candidate for TB. A clinical test should be performed in a future to ensure its safety as a therapeutic protein.
Mutation of katG in a clinical isolate of Mycobacterium tuberculosis: effects on catalase-peroxidase for isoniazid activation
Purkan1, Ihsanawati2, D. Natalia2, Y. M. Syah2,
D. S. Retnoningrum3, H. S. Kusuma4
1Biochemistry Research Division, Department of Chemistry,
Faculty of Sciences and Technology, Airlangga University; Surabaya, Indonesia;
e-mail: purkan@fst.unair.ac.id;
2Biochemistry Research Division, Faculty of Mathematics and Natural Sciences,
Bandung Institute of Technology, Bandung, Indonesia;
3School of Pharmacy, Bandung Institute of Technology, Bandung, Indonesia;
4Department of Chemical Engineering, Institut Teknologi
Sepuluh Nopember, Surabaya, Indonesia;
e-mail: heriseptyakusuma@gmail.com
Mutations in katG gene are often associated with isoniazid (INH) resistance in Mycobacterium tuberculosis strain. This research was perfomed to identify the katG mutation in clinical isolate (L8) that is resistant to INH at 1 μg/ml. In addition to characterize the catalase-peroxidase of KatG L8 and perform the ab initio structural study of the protein to get a more complete understanding in drug activation and the resistance mechanism. The katG gene was cloned and expressed in Escherichia coli, then followed by characterization of catalase-peroxidase of KatG. The structure modelling was performed to know a basis of alterations in enzyme activity. A substitution of A713G that correspond to Asn238Ser replacement was found in the L8 katG. The Asn238Ser modification leads to a decline in the activity of catalase-peroxidase and INH oxidation of the L8 KatG protein. The catalytic efficiency (Kcat/KM) of mutant KatGAsn238Ser respectively decreases to 41 and 52% for catalase and peroxidase. The mutant KatGAsn238Ser also shows a decrease of 62% in INH oxidation if compared to a wild type KatG (KatGwt). The mutant Asn238Ser might cause instability in the substrate binding site of KatG, because of removal of a salt bridge connecting the amine group of Asn238 to the carboxyl group of Glu233, which presents in KatGwt. The lost of the salt bridge in the substrate binding site in mutant KatGAsn238Ser created changes unfavorable for enzyme activities, which in turn emerge as INH resistance in the L8 isolate of M. tuberculosis.