Phylogenetic and immunological definition of four lipoylated proteins from Novosphingobium aromaticivorans, implications for primary biliary cirrhosis

• Published in: Journal of autoimmunity Vol. 24; no. 3; pp. 209 - 219
• Main Authors: Padgett, Kerstien A., Selmi, Carlo, Kenny, Thomas P., Leung, Patrick S.C., Balkwill, David L., Ansari, Aftab A., Coppel, Ross L., Gershwin, M. Eric
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.05.2005; Elsevier
• Subjects: Acyltransferases - genetics; Acyltransferases - immunology; Amino Acid Sequence; Animals; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Autoantigens - genetics; Autoantigens - immunology; Autoimmune Diseases - genetics; Autoimmune Diseases - immunology; Bacterial Proteins - genetics; Bacterial Proteins - immunology; Biological and medical sciences; Dihydrolipoyllysine-Residue Acetyltransferase; Evolution, Molecular; Fundamental and applied biological sciences. Psychology; Fundamental immunology; General aspects; Humans; Immunopathology; Lipoic acid; Lipoproteins - genetics; Lipoproteins - immunology; Liver Cirrhosis, Biliary - genetics; Liver Cirrhosis, Biliary - immunology; Medical sciences; Molecular mimicry; Molecular Mimicry - genetics; Molecular Mimicry - immunology; Molecular Sequence Data; Novosphingobium; Phylogeny; Protein homology; Pyruvate dehydrogenase; Pyruvate Dehydrogenase Complex - genetics; Pyruvate Dehydrogenase Complex - immunology; Sequence Homology, Amino Acid; Sphingomonadaceae - genetics; Sphingomonadaceae - immunology; Thioctic Acid - genetics; Thioctic Acid - immunology; Lipoic acid; Pyruvate dehydrogenase; Molecular mimicry; Protein homology; Autoimmunity; Immunopathology; Primary biliary cirrhosis; Enzyme; Pyruvate dehydrogenase (lipoamide); Definition; Hepatic disease; Homology; Phylogeny; Protein; Immunology; Digestive diseases; Oxidoreductases; EC 1.2.2.2; EC 1.2.4.1
• ISSN: 0896-8411; 1095-9157
• DOI: 10.1016/j.jaut.2005.01.012

Novosphingobium aromaticivorans, a unique ubiquitous bacterium that metabolizes xenobiotics and activates environmental estrogens, has been suggested as a pathogenic factor in the development of primary biliary cirrhosis (PBC). To define the molecular basis of PBC sera reactivity, we investigated the characteristic of the bacterial antigens involved. We cloned and sequenced four genes from N. aromaticivorans coding for immunoreactive proteins, arbitrarily named Novo 1 through Novo 4. We subsequently analyzed these proteins for their homology to known mitochondrial proteins and defined their reactivity using monoclonal antibodies (mAbs), rabbit anti-lipoic acid antibody, and PBC/control sera. Moreover, we studied their phylogenetic relation with the known PBC autoantigens. Novo proteins have an extraordinary degree of amino acid homology with all of the major human mitochondrial autoantigens PDC-E2 (Novo 1 and 2), OGDC-E2 (Novo 3), and BCOADC-E2 (Novo 4). Moreover, Novo 1–4 contain a lipoylated domain, are recognized by AMA-positive sera, and react with specific mAbs to mitochondrial antigens. Interestingly, the phylogenetic relation of the proteins emphasizes the conservation of the lipoylated domain. In conclusion, our data provide a high degree of confidence that N. aromaticivorans may potentiate the breakdown of self tolerance in genetically susceptible individuals.