[Immunocytochemical identification of tropomyosin in nucleoli and nucleolar matrix of Physarum polycephalum].

ABSTRACT

Nucleoli were isolated from physarum polycephalum, and nucleolar matrix was prepared by digesting the nucleoli respectively with DNase 1, 0.25 mol/L (NH4)2SO4 and 2 mol/L NaCl to remove DNA and most proteins. SDS-PAGE analysis indicated that there were about 20 polypeptides in nucleolar matrix component, including the 37 kD polypeptide which was similar to tropomyosin in molecular weight. The result of indirect immunofluorescence treated with anti-tropomyosin antibody and sheep anti-rabbit IgG antibody labelled with FITC showed that bright fluorescence was observed in the nucleoli and nucleolar matrix, but no bright fluorescence in the controls. Indirect Immunoblotting detection further verified that tropomyosin existed in nucleolar matrix. Protein A-colloidal gold immunoelectron microscopic study showed that there were many gold particles in the specimens labelled with tropomyosin antibody, and there were few gold particles found in the controls. Tropomyosin distributed dispersedly in nucleoli.