The NH2-terminal region of the P2 protein from rabbit sciatic nerve myelin.

The reaction of the P2 protein from rabbit sciatic nerve with CNBr produced four peptides: a 20-residue peptide (CN3) containing tryptophan which occupies the blocked NHZ terminus; Peptide CN1, a large peptide comprising over 70% of the P2 molecule; Peptide CN2, a fraction containing two tightly bound peptides having 2 half-cystine residues and comprising the COOH terminus; and Peptide CN4, a nonapeptide of the CN3 region obtained by abnormal CNBr cleavages of the bonds between Trp-8 and Lys-9 and Asp-17 and Asp-18, respectively.The complete sequence of Peptide CN3 was determined by sequenator and dansyl-monitored Edman procedures; the NHz-terminal sequence was shown to be N-Ac-Ser-Asn-Lys.Peptide CN3 is joined to Peptide CN1 by a Met-Lys linkage; an overlap peptide obtained by BNPS-skatole cleavage of the P2 protein between " p -8 and Lys-9 proved invaluable in linking Peptides CN3 abd CN1.We determined 44 and 33 residues, respectively, for Peptide CN1 and the BNPS-skatole peptide with a sequenator.These studies may bear on our understanding of allergic neuritis and Guillain-Barre syndrome since the P2 protein is an antigenic target in these diseases.Peptides CN1, CN2, and CN3 add up to 138 amino acids and account for the total P2 protein; the sequence of the first 64 residues of the P2 protein is: N-Ac-Ser-Asn-Lys-Phe-Leu-Gly-Thr-Trp-Lys-Leu-Val-Ser-Ser-Glu-Asn-Phe-Asp-Asp-Tyr-Met-Lys-Ala-Leu-Gly-Val-Gly-Leu-Ala-Thr-Arg-Lys-Leu-Gly-Asn-Leu-Ala-Lys-Pro-Asn-Val-Ile-Ile-Ser-Lys-Lys-Gly-Asp-Ile-Ile-Thr-Ile-Arg-Thr-Glu-Ser-Gly-Phe-Lys-Asn-Thr-Glu-Ile-Thr-Phe.