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ABSTRACT The effect of protein and chemical chaperones and crowders on thermal stability and aggregation of apoform of rabbit muscle glycogen phosphorylase b (apoPhb) has been studied at 37°C. Proline suppressed heat-induced loss in ability of apoPhb to reconstitution at 37°C, whereas α-crystallin did not reveal a protective action. To compare the antiaggregation activity of intact and crosslinked α-crystallins, an adsorption capacity (AC) of a protein chaperone with respect to a target protein was estimated. This parameter is a measure of the antiaggregation activity. Crosslinking of α-crystallin results in 11-fold decrease in the initial AC. The nonlinear character of the relative initial rate of apoPhb aggregation versus the [intact α-crystallin]/[apoPhb] ratio plot is indicative of the decrease in the AC of α-crystallin with increasing the [α-crystallin]/[apoPhb] ratio and can be interpreted as an evidence for dynamic chaperone structure and polydispersity of α-crystallin-target protein complexes. As for chemical chaperones, a semisaturation concentration of the latter was used as a characteristic of the antiaggregation activity. A decrease in the semisaturation concentration for proline was observed in the presence of the crowders (polyethylene glycol and Ficoll-70). © 2013 Wiley Periodicals, Inc. Biopolymers 101: 504-516, 2014. [ABSTRACT FROM AUTHOR]

Self-association of phosphorylase kinase (PhK) and its interaction with glycogen ( M=5500 kDa) and phosphorylase b (Ph b) has been studied using analytical ultracentrifugation and turbidimetry under the conditions of molecular crowding arising from the presence of high concentrations of osmolytes. In accordance with the predictions of the molecular crowding theory, trimethylamine N-oxide (TMAO) and betaine greatly favor self-association of PhK induced by Mg2+ and Ca2+ and PhK interaction with glycogen. In contrast, proline suppresses these processes, probably, due to its specific interaction with PhK. All osmolytes tested prevented the complex formation between PhK and its physiological substrate, Ph b. The specific interactions of PhK and Ph b with glycogen, in the living cell, presumably is a factor allowing the negative effect of crowding on the recognition of Ph b by PhK to be overcome. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The effect of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on thermal aggregation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from rabbit skeletal muscle at 45 degrees C has been studied using dynamic light scattering. In the presence of HP-beta-CD higher values of the rate of aggregation and larger aggregates were registered. The acceleration of GAPDH aggregation was due to destabilization of the enzyme molecule under the action of HP-beta-CD. This is evidenced by the data on thermal inactivation of GAPDH and differential scanning calorimetry., (Copyright 2010 Elsevier B.V. All rights reserved.)