A UBIQUITOUS PROTEIN IS THE SOURCE OF NATURALLY-OCCURRING PEPTIDES THAT ARE RECOGNIZED BY A CD8-CELL CLONE( T)

We previously isolated from mouse spleen an octapeptide (LSPFPFDL) tha t in association with the class I major histocompatibility complex pro tein L(d) is recognized by the antigen-specific receptor of an allorea ctive CD8+ T-cell clone (2C). Guided by an assay dependent upon the sa me 2C T-cell receptor, we have now isolated from the same source anoth er naturally occurring peptide. The second peptide (VAITRIEQLSPFPFDL) includes the entire octapeptide sequence and preliminary evidence sugg ests that it may be a natural precursor of the octapeptide. On finding extensive sequence homology between the 16-mer and part of human 2-ox oglutarate dehydrogenase, we determined the cDNA sequence of mouse 2-o xoglutarate dehydrogenase and found that the deduced amino acid sequen ce matches precisely the two naturally occurring peptides, indicating their origin by cellular processing of this ubiquitous self protein.