Identification of beta protein precursor in newborn rat brain

We have identified by protein sequencing the precursor of beta protein in newborn rat brain. A rabbit antibody was raised against a synthetic peptide corresponding to the carboxyl-terminal 30 residues (666-695) of the putative beta-amyloid protein precursor (Kang et al. 1987). The antiserum recognized multiple bands at 110-130 kD in the blot of Triton X-100 extract of newborn rat brain homogenates. The partially purified immunoreactive proteins were subjected to SDS-PAGE, electrophoretically transferred onto a polyvinylidene difluoride membrane and analyzed for the partial amino-terminal sequence. Each of the three major immunoreactive polypeptides yielded the same amino-terminal sequence of LEVPTxGNAgxL (x: unidentified, g: weakly assigned glycine) which corresponds to the residues 18-29 of the putative precursor.