Identification of the YMN-1 antigen protein and biochemical analyses of protein components in the mitochondrial nucleoid fraction of the yeast Saccharomyces cerevisiae

• Published in: Protoplasma Vol. 219; no. 1-2; pp. 51 - 58
• Main Authors: Sato, H, Tachifuji, A, Tamura, M, Miyakawa, I
• Format: Journal Article
• Language: English
• Published: Austria 01-02-2002
• Subjects: Acyltransferases - analysis; Acyltransferases - chemistry; Acyltransferases - immunology; Amino Acid Sequence; Antibodies, Monoclonal - immunology; Antigens, Fungal - analysis; Antigens, Fungal - chemistry; Antigens, Fungal - immunology; Dihydrolipoamide Dehydrogenase - analysis; Dihydrolipoamide Dehydrogenase - chemistry; Dihydrolipoamide Dehydrogenase - immunology; Electrophoresis, Gel, Two-Dimensional; Immunoblotting; Ketoglutarate Dehydrogenase Complex - analysis; Ketoglutarate Dehydrogenase Complex - chemistry; Ketoglutarate Dehydrogenase Complex - immunology; Mitochondria - enzymology; Mitochondria - immunology; Molecular Sequence Data; Molecular Weight; Protein Subunits; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - immunology; Saccharomyces cerevisiae Proteins - analysis; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - immunology
• ISSN: 0033-183X; 1615-6102
• DOI: 10.1007/s007090200005

We analyzed the protein components contained in the mitochondrial nucleoid (mt-nucleoid) fraction of the yeast Saccharomyces cerevisiae. Immunoblotting with anti-Abf2p antibody demonstrated the association of Abf2p, a major mitochondrial DNA-binding protein, with the mt-nucleoids. In contrast, porin and cytochrome c oxidase subunit III (CoxIIIp) were not detected by immunoblotting in the mt-nucleoid fraction. The YMN-1 monoclonal antibody recognized a 48 kDa protein of the mt-nucleoid fraction. The N-terminal amino acid sequence of the protein and immunological evidence showed that the YMN-1 monoclonal antibody recognizes dihydrolipoyl transsuccinylase (KE2), which is one of the constituents of the alpha-ketoglutarate dehydrogenase complex (KGDC). alpha-Ketoglutarate dehydrogenase (KE1) and dihydrolipoyl dehydrogenase (E3), which are other subunits of KGDC, were also detected in the mt-nucleoid fraction. An enzyme assay of the mt-nucleoid fraction showed that cytochrome c oxidase and fumarase activity were barely detected in the fraction, but the specific activity of KGDC in the mt-nucleoid fraction was relatively high and was approximately 60% of the specific activity in the mitochondrial fraction. Three components of KGDC were detected in the DNA-binding protein fractions after DNA-cellulose column chromatography of mt-nucleoid proteins. These results suggested that a part of KGDC in the mitochondrial matrix is associated with mt-nucleoids in vivo.