Physico-chemical properties of two point mutants of small heat shock protein HspB6 (Hsp20) with abrogated cardioprotectionстатья
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Дата последнего поиска статьи во внешних источниках: 7 октября 2020 г.
Аннотация:Physico-chemical properties of HspB6 S10F and P20L mutants with abrogated cardioprotective activityand associated with different forms of cardiomyopathy were analyzed. Under normal conditions both thewild-type HspB6 and its mutants formed small size oligomers (dimers) with apparent molecular weightof 50e60 kDa. Under crowding conditions (0.5 M trimethylamine N-oxide, TMAO) the wild-type HspB6remained predominantly dimeric or formed small molecular weight complexes, whereas both mutantstended to form high molecular weight complexes. Catalytic subunit of cAMP-dependent protein kinasephosphorylated the wild-type HspB6 and its S10F mutant with comparable rate. The rate of P20L mutantphosphorylation was higher than that of the wild-type HspB6. S10F and P20L mutations did not affectinteraction of phosphorylated HspB6 with universal adapter proteins 14-3-3. The wild-type HspB6 wasresistant to heat-induced denaturation and aggregation, whereas both its mutants were denatured andstarted to aggregate at temperature much lower than its wild-type counterpart. Titration with fluorescent probe bis-ANS was accompanied by larger increase of fluorescence in the case of both mutants than in the case of the wild-type HspB6. Both mutants possessed higher chaperone-like activity than the wildtype protein. It is concluded that both S10F and P20L mutations are accompanied by increase of hydrophobicity of the very N-terminal region of HspB6 leading to increased aggregation at elevated temperature, formation of large complexes under crowding conditions and increased chaperone-like activity measured in vitro. Increased hydrophobicity and self-association can affect substrate specificity and interaction with certain target proteins thus leading to decrease or complete abrogation of cardioprotectiveactivity.