Immunoreactivity of cytochrome c: antibodies to horse cytochrome c distinguish between sequence-related cytochromes only at the level of the 3-D-structure.
It has long been known that antibodies to cytochrome c can distinguish between closely sequence-related cytochromes c. Because the 3-D-structure of the polypeptide chain is virtually identical among eukaryotic cytochromes c, antibody specificity is directed against amino acid substitutions within a common polypeptide folding pattern. The question arises if the specificity is observed at the level of the 3-D-structure (conformational epitopes) and/or at the level of the primary structure (sequential epitopes). Using rabbit sera to horse cytochrome c, we show that discrimination against the host's own cytochrome c (six amino acid changes) occurs exclusively at the 3-D-level and not between peptides with sequences typical for horse and rabbit cytochrome c. Furthermore, deliberate immunization with horse apo-cytochrome c produces antibodies that cannot discriminate efficiently between sequence-related apo-cytochromes c. B-cell tolerance to the host's own protein seems to be restricted to the intact, native cytochrome. These findings bear on the application of antisera to distinguish between closely related proteins.
Leder
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Biochemisches Institut der Universität Zürich, Switzerland.
Bosshard
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HR
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002417:Cattle; D010856:Columbidae; D003574:Cytochrome c Group / Q000737:chemistry* / Q000276:immunology; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay; D006736:Horses; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011817:Rabbits
D000906:Antibodies; D003574:Cytochrome c Group