A heat-stable protein inhibitor of phosphoprotein phosphatase has been purified to homogeneity from rabbit liver extract by heating to 95 degrees followed by ion exchange chromatography on DEAE-cellulose and gel filtration on Sephadex G-200. The purified inhibitor showed a single band when examined by gel electrophoresis S20, w and Stokes radius values were 1.45 and 25.5, respectively. Using th...

Plasma membrane fractions I and II isolated from bovine corpus luteum contain phosphoprotein phosphatases. Enzyme activities associated with both membrane fractions showed pH optima in the neutral range and were most active with phosphoprotamine as the exogenous substrate. The enzyme activity was partially inhibited by Co2+, Zn2+ and Fe2+. Dithioerythritol, glutathione (reduced) and 2-mercaptoe...

Extracellular signaling is commonly mediated through post-translational protein modifications that propagate messages from membrane-bound receptors to ultimately regulate gene expression. Signaling cascades are ubiquitously intertwined, and a full understanding of function can only be gleaned by observing dynamics across multiple key signaling nodes. Importantly, targets within signaling cascad...

In the preceding paper, we demonstrated that the endogenous phosphorylation of a protein with a molecular weight of 29,000 was enhanced by various secretagogues in rat pancreatic and parotid lobules, the phosphorylation of this protein correlating both temporally and in a dose-dependent fashion with secretory protein discharge. In the present study, we established a specific methodology to char...

Ca has been found to increase the quantity of (32)P incorporated into red cell ghosts from [gamma-(32)P]ATP over the levels obtained by incubation with Mg alone or with Mg + Na, in correlation with the effect of Ca on the associated ATPase activities. When the (32)P-labeled ghosts were solubilized in sodium dodecyl sulfate (SDS) and electrophoresed on acrylamide gels only two bands could be det...

Phosphorylation is an important post-translational protein modification with regulatory roles in diverse cellular signaling pathways. Despite recent advances in mass spectrometry, the detection of phosphoproteins involved in signaling is still challenging, as protein phosphorylation is typically transient and/or occurs at low levels. In green plant tissues, the presence of highly abundant prote...

The immunohistochemical detection and quantification of phosphoprotein levels can provide valuable information regarding the activation of cell signaling pathways within tumor samples, with potential implications for prognosis and treatment selection. However, phosphoprotein levels may be affected by clinical tissue handling, hypoxia and other cellular stressors prior to tissue fixation. The pr...

The phosphoprotein DARPP-32 (dopamine and cyclic adenosine 3´, 5´-monophosphate-regulated phosphoprotein, 32 kDa) is an important component in the molecular regulation of postsynaptic signaling in neostriatum. Despite the importance of this phosphoprotein, there is as yet little known about the nanoscale distribution of DARPP-32. In this study we applied superresolution stimulated emission depl...