Journal
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
Volume 76, Issue -, Pages 86-93Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ijbiomac.2015.02.022
Keywords
alpha B-Crystallin; Oligomeric state; Chaperone-like activity; Aggregation; Crowding; Ca2+, Mg2+ ions
Funding
- Russian Foundation for Basic Research [14-04-01530-a, 14-04-00146-a]
- Program Molecular and Cell Biology of the Presidium of the Russian Academy of Sciences
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The main function of small heat shock proteins acting as suppressors of aggregation of non-native proteins is greatly influenced by crowded environment in the cell and the presence of divalent metal ions. The goal of the present work was to study the effects of Ca2+ and Mg2+ ions on the quaternary structure and anti-aggregation activity of alpha B-crystallin under crowding conditions. We showed that Ca2+ and Mg2+ ions induced formation of suboligomeric forms of alpha B-crystallin. This effect was retained in the presence of crowder (polyethylene glycol), although to a lesser degree. The chaperone-like activity of alpha B-crystallin was analyzed using heat-induced aggregation of myosin subfragment 1 (Si) at 40 degrees C. In the absence of crowding agents chaperone-like activity of alpha B-crystallin exhibited low sensitivity to the presence of Ca2+ and Mg2+ ions. The addition of the crowding agents (polyethylene glycol 20000, Ficoll 70) dramatically increased Si aggregation rates and significantly depressed anti-aggregation activity of alpha B-crystallin. Low concentrations of Ca2+ (0.1 mM) and Mg2+ (10 mM) partially restored the chaperone-like activity of alpha B-crystallin in the presence of crowders. This effect was observed at relatively low values of [alpha B-crystallin]/[S1] molar ratio, however, at [alpha B-crystallin]/[S1]>0.2 the stimulating effect of Ca2+ became less pronounced. These findings might indicate that under crowded cell conditions different factors, including divalent cations, can effectively modulate chaperone-like activity of protein chaperones, which otherwise cannot properly cope with crowding-provoked accelerated rates of substrates aggregation. (C) 2015 Elsevier B.V. All rights reserved.
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