DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.48120#0065
Abstracts
47
was represented by two major polypeptides, 70-74 kDa and 45-52 kDa. In 1987
the molecular cloning of a cDNA sequence for an M2 antigen was reported, by
antibody screening of a cDNA expression library (Agtll). The cloned DNA
(1370 bp) coded for a polypeptide which expressed the antigenic reactivity of the
70-74 kDa antigen. The amino acid sequence of the 70-74 kDa polypeptide was
found to correspond with that of the E2 subunit of the mitochondrial pyruvate
dehydrogenase (PDH) enzyme complex. PDH is a member of a family of three
enzymes, the 2-oxo-acid dehydrogenases; the others are branched-chain, 2-oxo-
acid dehydrogenase and 2-oxo-glutaric dehydrogenase and these contribute to the
45-52 kDa antigenic reactivity on Western blotting with PBC sera. These en-
zymes are abundant in nature and there are provocative sequence homologies in
yeast and bacteria.
Deductions based on sequence conservation, and studies by absorption of an-
tibody activity by synthetic peptides, placed an autoepitope (major immunogenic
region) of PHD-E2 at residues 83-92, these being ile-glu-thr-asp-lys-ala-thr-ile-
gly-phe-(IETDKATIGF). The lysine is the point of attachment of a prosthetic
group, lipoic acid, essential for the function. The immunochemical reactions of
PBC sera have a functional correlate in that diluted sera (1/50) will very rapidly,
and with high specificity, inhibit the catalytic activity of the PDH enzyme on the
natural substrate pyruvate, using a spectrophotometric readout of the formation
of NADH. Rabbits immunized with the recombinant M2 protein, and Lewis rats
immunized with a synthetic peptide corresponding to the autoepitope IET-
DKATIGF, produced mitochondrial antibodies, but these sera did not inhibit
PDH enzyme activity.
Thus there is evidence for a conformational or site difference in the epitope
for natural and experimentally induced antibodies to the M2 mitochondrial
(PDH-E2) autoantigen of PBC.
Molecular Biological Identification of Autoantigens in Autoimmune
Hepatitis - Relevance for Pathogenesis, Diagnosis, and Treatment
M. P. Manns
Dept, of Medicine I, University of Mainz, Mainz, FRG
Several autoantigens are recognized by circulating autoantibodies in autoim-
mune liver diseases. Screening of cDNA libraries with human autoantibodies led
to the molecular cloning of mitochondrial autoantigens in primary biliary cir-
47
was represented by two major polypeptides, 70-74 kDa and 45-52 kDa. In 1987
the molecular cloning of a cDNA sequence for an M2 antigen was reported, by
antibody screening of a cDNA expression library (Agtll). The cloned DNA
(1370 bp) coded for a polypeptide which expressed the antigenic reactivity of the
70-74 kDa antigen. The amino acid sequence of the 70-74 kDa polypeptide was
found to correspond with that of the E2 subunit of the mitochondrial pyruvate
dehydrogenase (PDH) enzyme complex. PDH is a member of a family of three
enzymes, the 2-oxo-acid dehydrogenases; the others are branched-chain, 2-oxo-
acid dehydrogenase and 2-oxo-glutaric dehydrogenase and these contribute to the
45-52 kDa antigenic reactivity on Western blotting with PBC sera. These en-
zymes are abundant in nature and there are provocative sequence homologies in
yeast and bacteria.
Deductions based on sequence conservation, and studies by absorption of an-
tibody activity by synthetic peptides, placed an autoepitope (major immunogenic
region) of PHD-E2 at residues 83-92, these being ile-glu-thr-asp-lys-ala-thr-ile-
gly-phe-(IETDKATIGF). The lysine is the point of attachment of a prosthetic
group, lipoic acid, essential for the function. The immunochemical reactions of
PBC sera have a functional correlate in that diluted sera (1/50) will very rapidly,
and with high specificity, inhibit the catalytic activity of the PDH enzyme on the
natural substrate pyruvate, using a spectrophotometric readout of the formation
of NADH. Rabbits immunized with the recombinant M2 protein, and Lewis rats
immunized with a synthetic peptide corresponding to the autoepitope IET-
DKATIGF, produced mitochondrial antibodies, but these sera did not inhibit
PDH enzyme activity.
Thus there is evidence for a conformational or site difference in the epitope
for natural and experimentally induced antibodies to the M2 mitochondrial
(PDH-E2) autoantigen of PBC.
Molecular Biological Identification of Autoantigens in Autoimmune
Hepatitis - Relevance for Pathogenesis, Diagnosis, and Treatment
M. P. Manns
Dept, of Medicine I, University of Mainz, Mainz, FRG
Several autoantigens are recognized by circulating autoantibodies in autoim-
mune liver diseases. Screening of cDNA libraries with human autoantibodies led
to the molecular cloning of mitochondrial autoantigens in primary biliary cir-