A placental polypeptide activator of a membranous protein kinase and its relation to histone 1.

Abstract
Crude transforming growth factor preparations of human placenta contain a polypeptide that is required for the activity of a protein kinase purified from plasma membrane preparations of Ehrlich ascites tumor cells. The kinase activator was separated from transforming growth factor-.beta. by reversed-phase high-performance liquid chromatography and affinity chromatography. Like the transforming growth factor, it is heat stable and trypsin labile, but it is not inactivated by dithiothreitol. In sodium dodecyl sulfate/polyacrylamide gel electrophoresis the purified preparation shows a major double band at about 31,000 daltons. Comparisons of electrophoretic mobility, protein kinase stimulatory activity, and cross-reactivity with an antibody against histone 1 suggest that the placental activator is identical with histone 1.