Phosphorylation of proteins in cultured human placenta
Galski H., Weinstein D., Gileadi O.
The in vitro phosphorylation of proteins in human first trimester and term placental tissues have been studied. The data show the following: There is a difference in the apparent phosphorylation rate between early and term placentas which cannot be explained by changes in the level and the specific radioactivity of the cellular ATP pool. Some proteins are exclusively phosphorylated in the placenta early in gestation, while others are phosphorylated at the end of gestation and could not be detected in first trimester placenta. In first trimester placenta phosphorylation occurs predominantly on threonine residues; term placenta exhibits a significant relative increase in the transfer of radioactive phosphate to serine residues.