ALLERGIC ENCEPHALOMYELITIS - CLEAVAGE OF C-TRYPTOPHYL BOND IN ENCEPHALITOGENIC BASIC PROTEINFROM BOVINE MYELIN

The presence of one tryptophan residue in the encephalitogenic A1 protein from bovine spinal cord was established by six independent techniques. A nonencephalitogenic peptide containing 55 amino acid residues was derived from the A1 protein by cleavage of the C-tryptophyl bond with N-bromosuccinimide. This peptide, referred to as peptide T, was purified by gel filtration and Cellex-P chromatography and obtained in 31% yield. It appeared homogeneous by polyacrylamide gel and paper electrophoresis. The structure of peptide T was partially determined as follows: H-Gly-Ala-Glu-Gly-Gln-Ser-Pro-Phe-Gly-Lys....Ala-Arg-Arg-OH. The amino acid sequence of the N-terminal region is identical with that portion of the sequence of the encephalitogenic peptide E, a peptide obtained from pepsin hydrolysis of the A1 protein, which contains a tryptophan-glycine linkage. The H-Ala-Arg-Arg-OH sequence, established with carboxypeptidases A and B, is identical with that of the A1 protein and thus identifies peptide T as the 55 residues of the C-terminal region of the A1 polypeptide chain. The molecular weight of 5750 daltons was determined by amino acid analysis and confirmed by peptide mapping of the tryptic digest which showed 13 peptides (12 expected), 5 of which contain arginine. Peptide T, like the A1 protein, is highly basic and contains a total of 13 lysine, histidine, and arginine residues. The molecular weight falls close to that determined by quantitation of the PTH-glycine obtained by Edman degradation. Peptide T does not induce experimental allergic encephalomyelitis, even at 100 μg per guinea pig, and further emphasizes the importance of the tryptophan residue and the adjacent polypeptide region for determining encephalitogenic activity. © 1969.