Determination of phosphorylase kinase activity in crude homogenates by affinity chromatography on 5'-AMP sepharose

Aptamer-Based Affinity Chromatography for Protein Extraction and Purification

Aptamers are oligonucleotide molecules able to recognize very specifically proteins. Among the possible applications, aptamers have been used for affinity chromatography with effective results and advantages over most advanced protein separation technologies. This chapter first discusses the context of the affinity chromatography with aptamer ligands. With the adaptation of SELEX, the chemical modifications of aptamers to comply with the covalent coupling and the separation process are then extensively presented. A focus is then made about the most important applications for protein separation with real-life examples and the comparison with immunoaffinity chromatography. In spite of well-advanced demonstrations and the extraordinary potential developments, a significant optimization work is still due to deserve large-scale applications with all necessary validations. Graphical Abstract Aptamer-protein complexes by X-ray crystallography.

Aptamer affinity ligands in protein chromatography

The present review deals with the place of single chain oligonucleotide ligands (aptamers) in affinity chromatography applied to proteins. Aptamers are not the only affinity ligands available but they represent an emerging and highly promising route that advantageously competes with antibodies in immunopurification processes. A historical background of affinity chromatography from the beginning of the discipline to the most recent outcomes is first presented. Then the focus is centered on aptamers which represent the last step so far to the long quest for affinity ligands associating very high specificity, availability and strong stability against most harsh cleaning agents required in chromatography. Then technologies of ligand selection from large libraries followed by the most appropriate chemical grafting approaches are described and supported by a number of bibliographic references. Experimental results assembled from relevant published paper are reported; they are selected by their practical applicability and potential use at large scale. The review concludes with specific remarks and future developments that are expected in the near future to turn this technology into a large acceptance for preparative applications.

Activation of the glycogenolytic cascade in human polymorphonuclear leucocytes by different phagocytic stimuli

Human polymorphonuclear leucocytes were found to respond to activation by immunoglobulin opsonized latex particles and to complement opsonized zymosan particles with a rapid transient increase in cAMP concentration, dissociation of the cAMP dependent protein kinase, activation of glycogen phosphorylase and glycogen break down. However, since phosphorylase kinase was not activated, the activation of phosphorylase is believed to be secondary to non-covalent activation of phosphorylase kinase by Ca2+. Activation by the soluble stimulator phorbol myristate acetate resulted in activation of phosphorylase and glycogen break down, whereas no changes in cAMP concentration, protein kinase activity, or phosphorylase kinase activity were observed. The activation of phosphorylase is ascribed to an increase in cytosolic Ca2+ concentration. The response to stimulation by zymosan was strongly inhibited by ethylene glycol-bis-(beta-aminoethyl ether)-N,N1-tetraacetic acid, which did not affect stimulation by either latex particles or phorbol myristate acetate. The same differential effect of ethylene glycol-bis(beta-aminoethyl ether)-N,N1-tetraacetic acid was observed when the response of the cells was measured as increase in oxygen consumption and activation of the hexose monophosphate shunt.

Effect of glycogenolytic agents on glycogen synthase activity in polymorphonuclear leukocytes. Evidence for a Ca2+-mediated regulation of glycogen synthase activity

Human polymorphonuclear leukocytes were found to respond to the beta-receptor activators, adrenalin and isoproterenol, with a rapid transient increase in cyclic AMP, activation of cyclic AMP-dependent protein kinase, phosphorylase kinase, deactivation of glycogen synthase and glycogen breakdown. This response was unaffected by the presence of 10 mM EGTA. Incubation of leukocytes with phorbol myristate acetate, which stimulates the hexose monophosphate shunt by a Ca2+ mediated mechanism, resulted in activation of phosphorylase without affecting cyclic AMP-dependent protein kinase or phosphorylase kinase activity, thus indicating a Ca2+-mediated activation of phosphorylase. This was, however, unaffected by EGTA. Prolonged incubation with phorbol myristate acetate was found to result in a parallel activation of phosphorylase and glycogen synthase secondary to a pronounced depletion of cellular glycogen. Addition of glucose to polymorphonuclear leukocytes resulted in total conversion of phosphorylase a to the b form and activation of glycogen synthase, however, when EGTA was included, the response to glucose was greatly amplified, thus indicating the synthase conversion is regulated by Ca2+ sensitive mechanisms which do not involve phosphorylase kinase. Addition of adrenalin to cells previously activated by glucose resulted in an increase in the concentration of cyclic AMP and activation of cyclic AMP-dependent protein kinase but deactivation of synthase was not effectuated under these conditions.