Isolation, Sequence, and Developmental Profile of a Brain-Specific Polypeptide, PEP-19

By comparing the HPLC profiles of cerebellar extracts from adult and neonatal rats, a developmentally regulated polypeptide, termed PEP-19, was identified. The concentration of PEP-19 rose from 0.1 nmol/g of cerebellum at birth to 2 nmol/g at 20 days postpartum. The polypeptide could also be detected at lower levels in olfactory bulbs of adult rats but was absent in cerebral cortex, brain stem, and all non-neural tissues examined. HPLC-purified PEP-19 contained 61 amino acids and had a molecular size of 7.6 kDa. The native polypeptide is blocked at its amino terminus but was sequenced following proteolytic and chemical fragmentation. The primary amino acid sequence was determined to be: X (S-E) R Q S A G A T N G K D K T S G D N D G Q K K V Q E E F D I D M D A P E T E R A A V A I Q S Q F R K F Q K K K A G S Q S. PEP-19 has a unique sequence, but shares some homology with several calcium binding proteins including the β chain of S100 and intestinal calcium binding protein. This polypeptide is the primary translation product of cerebellar poly(A)+mRNA.