Allergic encephalomyelitis: Isolation and characterization of encephalitogenic peptides from the basic protein of bovine spinal cord

Abstract

The basic protein encephalitogen from bovine spinal cord was digested with pepsin for 2 hr; the resulting digest was subjected to gel filtration on a column of Sephadex G-25-G-75. Peptide families obtained in this way were highly encephalitogenic. Upon fractionation of the peptides on a column of Cellex-P, 19 peptides were obtained as demonstrated by high-voltage electrophoresis. After desalting of specific peptides on a column of Sephadex G-10-G-25 11 homogeneous peptides were isolated. The data showed that two of these peptides, referred to as E (16 amino acid residues) and E1 (26 amino acid residues), are more potent in inducing EAE in guinea pigs than the original A1 protein. The amino acid composition of Peptide E and E1 were similar; each contained one tryptophan residue, the only one found in the A1 protein (142 residues). Serine was identified as the N-terminal amino acid of Peptides E and E1 and also Peptide D which contains tryptophan, but is nonencephalitogenic. The results indicate that these peptides originate from the same region of the A1 molecule, and support the previous proposal that the EAE determinant is the property of the primary structure of the A1 protein as defined by the specific amino acid sequence of Peptide E.