Cdk5 phosphorylation of human PrP23–231 at S43. A, Autoradiogram of Cdk5 in vitro kinase assay on PrP23–231 or Tau protein. B, Coomassie blue stain of PrP and Tau protein. C, Autoradiogram of in vitro Cdk5 kinase assay on PrP in the absence or presence of olomoucine (Olo.). D, Autoradiogram and Coomassie blue stain of in vitro Cdk5 kinase assay on PrP and PrP S43A. E, Western blot with anti-pPrPS43 antiserum and anti-PrP109–112 3F4 antibody of 100 ng of nonphosphorylated PrP or 100 ng of Cdk5 pPrP. F, Western blot with 3F4 antibody of PrP and pPrP immunoprecipitated (IP) with anti-pPrPS43 or anti-PrP36–56 R155 antisera. G, Western blot with 3F4 and anti-pPrPS43 of Cdk5 kinase assay on PrP or PrP S43A.