PEPTIDE-MAPPING OF MAMMALIAN BRAIN PROTEIN-H(3) IN SUBSETS OF TISSUESAND LIGAND-BINDING STUDIES

In this report the structure of the novel polypeptide h3, isolated fro m subsets of tissues of a single species, and the structural similarit y between interspecies h3 were investigated by peptide mapping of enzy matic and chemical cleavage fragments of h3 in one-dimensional SDS-PAG E; the peptide maps were commented on in comparison with the known seq uence of 21 kDa protein, a h3-like ox brain protein. The following res ults were obtained : peptides generated by chymotrypsin, protease XX, BNPS-skatole and CNBr cleavage of different tissues in a single specie s were strikingly identical, whereas peptide maps obtained from analog ue tissue in different species revealed slight structural differences. Possible ligand-h3 binding was studied by comparing the c.d. spectra of native h3, and h3 incubated with several phospholipids. Given the p resence of h3 or h3-like protein in rat and human platelets, h3 was al so assessed in platelet aggregation in the presence of h3 and specific anti-h3 antserum. So far, the results emphasize the unique intra- and interspecies molecular form of h3, allow us to assign to known amino acid sequence of 21 kDa to a large extent to human h3, but do not iden tify h3 as a phospholipid binding protein.