Abstract
We studied the proteins expressed specifically in the fetal rat brain to clarify the changing mechanism of the central nervous system from birth to death. Regarding the process for investigation of putative“human-leukocyte associated (HLA) ”Class II associated proteins (PHAP and II) which were speculated as components of the signal pathway, we reported the detection of PHAP I protein kinase activities in the PHAP II binding protein fraction of fetal rat brain cytosol and that PHAP I protein was phosphorylated mainly on the Serine residue. In this stady, we examined PHAP I kinase using mutants of PHAP I which were deleted amino acids and the procedure for detection of protein kinase activities toward protein substrates included in gels. In the phosphorylated site of PHAP I was 204 of serine residue in the highly acidic C-terminal region of the PHAP I amino acid sequence. The molecular mass of PHAP I kinase were 37kDa and 39kDa, and gel filtration chromatography suggested that PHAP I kinase was larger in vivo. PHAP I kinase has not been identified yet, however, we speculate that PHAP I kinase is one of the components of the signal pathway because the phosphorylation site is in the neighborhood of the sequence requirement for synthetic peptide-mediated translocation to the nucleus.
