Immunological characterization of a human homolog of the 65-kilodalton mycobacterial antigen.
A human mitochondrial protein, designated P1 (63 kilodaltons [kDa], shows extensive sequence homology (47% identical residues and an additional approximately 20% conserved changes) to the 65-kDa mycobacterial antigen. To understand the relationship of these proteins, the cross-reactivity of several monoclonal antibodies directed against the 65-kDa Mycobacterium leprae antigen towards human, Chinese hamster, chicken, and bacterial cells has been examined. A number of antibodies (Y1-2, ML 30-A2, and F47-9-1) were found to cross-react with a 63-kDa antigen in vertebrate cell extracts and stained mitochondria in immunofluorescence studies. Some of these antibodies also reacted with a P1-beta-galactosidase fusion protein in recombinant Escherichia coli cells, expressing part of the human P1 protein. These results provide strong evidence that P1 is the mammalian homolog of the 65-kDa antigen. The human P1 protein also shows significant similarity (P less than 0.001) to a number of other bacterial and viral proteins including the pol polyprotein of human immunodeficiency viruses and the penicillin-binding protein of Neisseria gonorrhoeae. The observed similarity between human P1 protein and the major antigenic proteins of pathogenic organisms (e.g., 60- to 65-kDa mycobacterial antigen) suggests its possible involvement in autoimmune diseases (e.g., rheumatoid arthritis) by antigenic mimicry.
Dudani
A K
AK
Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada.
Gupta
R S
RS
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000032:analysis* / Q000276:immunology; D002642:Chick Embryo; D006224:Cricetinae; D003429:Cross Reactions; D004926:Escherichia coli / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009166:Mycobacterium leprae / Q000276:immunology*; D012486:Salmonella typhimurium / Q000276:immunology; D012689:Sequence Homology, Nucleic Acid
D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial