The Identification of proteins present in culture filtrare of Mycobacterium tuberculosis DT and comparison with human tuberculin proteins by electrophoretic methods

Background and objectives: Tuberculin is the proteins existed intuberculosis culture medium which precipitated by trichloroacetic acid (TCA)or ammonium sulfate. Tuberculin is used for diagnosis of Tuberculosis. Theaim of this study is to compare the human tuberculin produced by RaziInstitute and Mycobacterium tuberculosis Culture Filtrate Protein.Material and Methods: Initially By biphasic medium, Bacteria fromLowenstein–Jensen solid medium was transferred to a Dorset Henley Liquidmedium. After 6 weeks of growth, the bacteria were isolated from liquidmedium containing secretory proteins by the 0, 22 micron filter and thesolution containing secretory proteins was precipitated by TCA andammonium sulfate, separately. Then, using spectrophotometer and kjeldahlprotein assay, the presence of protein in solution was confirmed. At the end,the precipitated proteins are compared with the human tuberculin byCoomassie-Blue stained SDS-PAGEResults: The protein samples precipitated by TCA have more bands in thelimit of higher than 20 kDa, but the protein samples by ammonium sulfatehave more bands in the limit of less than 20 kDa. Human tuberculin proteinsare like smear and their weight is less than 16 kDa.Conclusion: It seems that ammonium sulfate is more suitable for lowmolecular weight proteins than TCA for precipitation.Key words: Mycobacterium tuberculosis, SDS-PAGE, tuberculin