Protein kinase C, an enzyme that is activated by the receptor-mediated hydrolysis of inositol phospholipids, relays information in the form of a variety of extracellular signals across the membrane to regulate many Ca2+-dependent processes. At an early phase of cellular responses, the enzyme appears to have a dual effect, providing positive forward as well as negative feedback controls over various steps of its own and other signaling pathways, such as the receptors that are coupled to inositol phospholipid hydrolysis and those of some growth factors. In biological systems, a positive signal is frequently followed by immediate negative feedback regulation. Such a novel role of this protein kinase system seems to give a logical basis for clarifying the biochemical mechanism of signal transduction, and to add a new dimension essential to our understanding of cell-to-cell communication.

https://science.sciencemag.org/content/sci/233/4761/305.full.pdf

Studies and perspectives of protein kinase C

Consensus sequences as substrate specificity determinants for protein kinases and protein phosphatases.

Protein phosphorylation is now recognized to be the major general mechanism by which intracellular events in mammalian tissues are controlled by external physiological stimuli However, only recently has the idea that different cellular functions are controlled by common protein kinases and protein phosphatases started to gain widespread acceptance Thus there is an integrated network of regulatory pathways, mediated by phosphorylation-dephosphorylation, that allows diverse cellular events to be coordinated by neural and hormonal stimuli The evidence that supports this concept is reviewed, with emphasis on the role of protein phosphorylation in enzyme regulation

The role of protein phosphorylation in neural and hormonal control of cellular activity

Publisher Summary This chapter presents a table of phosphorylation site sequences for protein-serine/threonine and protein-tyrosine kinases. Over 240 phosphorylation site sequences along with the phosphorylated residue(s) are included in this table. The chapter presents another table containing consensus phosphorylation site motifs for each enzyme. The frequencies listed in this table are derived from the first table, unless indicated otherwise. The S : T ratio is for the total number of phosphorylation sites.

Protein kinase phosphorylation site sequences and consensus specificity motifs: tabulations.

Role of multiple basic residues in determining the substrate specificity of cyclic AMP-dependent protein kinase.

Non-dependence on native structure of pig liver pyruvate kinase when used as a substrate for cyclic 3′,5′-AMP-stimulated protein kinase

Amino acid sequence at the phosphorylated site of rat liver phenylalanine hydroxylase and phosphorylation of a corresponding synthetic peptide

Phosphorylation of human fibrinogen in vitro with calcium-activated, phospholipid-dependent protein kinase and [32P]ATP

Amino acid sequence at the phosphorylated site of rat liver fructose-1,6-diphosphatase and phosphorylation of a corresponding synthetic peptide.

Publisher Summary This chapter focuses on the detection and identification of substrates for protein kinases active on serine and threonine residues, with emphasis on the substrates and kinases present in mammalian tissues. The crude tissue extract may consist in isolated cell supernatant or the extracts of particulate cell fractions. When the extracts are incubated with [γ-32P]ATP and Mg 2+ , considerable incorporation of [32P]phosphate into proteins occurs, owing to the presence of protein kinases and endogenous substrates. The method of the interruption of phosphorylation greatly influences the amount and type of [32P]phosphoproteins obtained. When further studies on native phosphoprotein are to be made, the reaction may be interrupted by the removal of free Mg 2+ with ethylenediaminetetraacetic acid (EDTA). Phosphoprotein phosphatases may be inhibited by sodium fluoride or orthophosphate. The 32P-labeled phosphoproteins are separated from most of the low molecular weight, 32P-labeled compounds by rapid gel filtration. The considerable amount of these compounds may be adsorbed to the protein of crude extracts after the gel filtration. To obtain reliable estimates of the true protein phosphorylation, the adsorbed material must be removed by denaturation procedures.

Elisabet Humble

Papers

Non-dependence on native structure of pig liver pyruvate kinase when used as a substrate for cyclic 3′,5′-AMP-stimulated protein kinase

Amino acid sequence at the phosphorylated site of rat liver phenylalanine hydroxylase and phosphorylation of a corresponding synthetic peptide

Phosphorylation of human fibrinogen in vitro with calcium-activated, phospholipid-dependent protein kinase and [32P]ATP

Amino acid sequence at the phosphorylated site of rat liver fructose-1,6-diphosphatase and phosphorylation of a corresponding synthetic peptide.

Detection and identification of substrates for protein kinases: Use of proteins and synthetic peptides