| Abstract: | In the Lewis rat, fragment 43–88 of the highly encephalitogenic guinea-pig basic protein has been previously shown to retain the full activity of the parent protein. In the present studies this fragment was subjected to controlled chymotryptic digestion so that cleavage occurred only at tyrosine 67, generating two peptides, residues 43-67 and residues 68-88. When compared on an equimolar basis peptide 68-88 had the same encephalitogenic activity as the intact fragment and induced the same degree of immunologically specific cell response as measured by the in vitro lymphocyte stimulation test. Peptide 68-88 was further fragmented by selective tryptic cleavage at arginine 78 after blocking lysine 73 with citraconic anhydride. The two peptides, residues 68-78 and residues 79-88, were not encephalitogenic, indicating that residues adjacent to the point of cleavage contribute to the active site. |
