The effects of histones on the enzymatic phosphorylation of nuclear phosphoproteins have been extensively studied in vitro. Histones cause a 5to Io-fold increase in the rate and extent of phosphorylation of nuclear phosphoprotein, with the lysinerich histones being the most effective at stimulation. Evidence suggests that the histones are not being phosphorylated themselves, but rather act to m...

An acidic nucleolar phosphoprotein with a subunit M(r) of 70,000 was purified as an apparent dimer of 139,000 from isolated nuclei of the slime mold Physarum polycephalum. The protein was purified without the aid of strong dissociating agents after its selective phosphorylation in isolated nuclei by a polyamine-mediated reaction. Its amino acid composition resembled that of a nucleolar phosphop...

The phosphoproteins formed by incubation of red cell ghosts with [gamma-(32)P]ATP in the presence of Mg and Na + Mg have been characterized by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The (32)P-labeled phosphoprotein was seen as a single peak confined to the region of the diffuse 90,000 dalton polypeptide band; labeling with Na + Mg considerably increased the quantity of...

Preanalytical conditions applied during sample collection and processing can affect the detection or quantification of unstable phosphoprotein biomarkers. We evaluated the consequences of tissue stabilization and protein extraction methods on phosphoprotein analysis. The effects of stabilization techniques (heat stabilization, snap-freezing) and time on the levels of phosphoproteins, including ...

This paper summarizes our work performed with glucocorticoid-binding complexes in molybdate-stabilized cytosol prepared from 32P-labeled L-cells. In our early work, we showed that cytosol prepared from 32P-labeled L-cells contains two phosphoproteins (a 90 and a 98-100 kdalton protein) that elute from an affinity resin of deoxycorticosterone agarose in a manner consistent with the predicted beh...

The ability of legume crops to fix atmospheric nitrogen via a symbiotic association with soil rhizobia makes them an essential component of many agricultural systems. Initiation of this symbiosis requires protein phosphorylation-mediated signaling in response to rhizobial signals named Nod factors. Medicago truncatula (Medicago) is the model system for studying legume biology, making the study ...

The phosphoprotein phosphatase(s) acting on muscle phosphorylase a was purified from rabbit liver by acid precipitation, high speed centrifugation, chromatography on DEAE-Sephadex A-50, Sephadex G-75, and Sepharose-histone. Enzyme activity was recovered in the final step as two distinct peaks tentatively referred to as phosphoprotein phosphatases I and II. Each phosphatase showed a single broad...

The calcium transport protein of the sarcoplasmic reticulum accepts inorganic phosphate rapidly when phosphorylation is initiated either by the addition of phosphate or magnesium ions to the calcium free protein. Phosphorylation proceeds much more slowly when it is initiated by the addition of the calcium chelatro ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) to the ph...

Oncornaviruses, which contain a virion-associated protein kinase, were found to possess phosphoproteins as virion structural components. One major phosphoprotein common to strains of laboratory and wild mouse oncornaviruses and a strain of feline leukemia virus was shown to be a polypeptide of about 12, 000 mol wt. In addition to this, the Kirsten strain of murine sarcoma virus contained a seco...