Isolation and Partial Characterization of an 80,000‐Dalton Protein Kinase from the Micro vessels of the Porcine Brain

A novel serine/threonine-specific protein kinase was isolated from the microvessels of porcine brains. The molecular mass of the protein is 80,000 daltons, as judged by gel electrophoresis under denaturing conditions, or 122,000 daltons, on high-resolution gel permeation chromatography in the native state. The activity of this enzyme is stimulated by various histones or polyamines, like spermine or spermidine, but not by any of the common second messengers. The amino-terminal sequence data show no homologies to any of the published kinases, but rather to a heat-shock protein of unknown function.