Small heat-shock proteins (sHSPs) are ATP-independent molecular chaperones that engage with partially unfolded proteins to avoid abnormal aggregation, demonstrating chaperone-like activity in the process. The chaperone-like activity of sHSPs is influenced by the dynamics of the quaternary structure. The link between the dynamic structure of sHSPs and their chaperone-like activity, on the other hand, is still poorly understood. Temperature, ions, a target protein, crowding, and other variables all affect the structure and activity of sHSPs. The effect of crowding on sHSP activity has received the least attention. In this study, the chaperone-like activity of HSPB5 was quantified using dynamic light scattering using two test systems: heat-induced aggregation of muscle glycogen phosphorylase b (Phb) at 48°C and dithiothreitol-induced aggregation of -lactalbumin at 37°C. The oligomeric state of HSPB5 and target proteins was monitored by analytical ultracentrifugation. The role of suboligomeric variants of HSPB5 in anti-aggregation is explored. Using Phb as a target protein, the effect of crowding on HSPB5 anti-aggregation activity was investigated. Under crowded settings, the duration of the nucleation stage was observed to decrease in tandem with an increase in the relative rate of aggregation of Phb in the presence of HSPB5. The activity of sHSPs may be sensitively modulated by crowding. Biopolymers (proteins) that can vary the level of excluded volume in cells by reversibly modifying the state of association/dissociation or accepting an expanded or compact state of the quaternary structure can also do so.
Author (s) DetailsNatalia A. Chebotareva
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
Svetlana G. Roman
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
Vera A. Borzova
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
Tatiana B. Eronina
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
Valeriya V. Mikhaylova
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
Boris I. Kurganov
Bach Institute of Biochemistry, Federal Research Centre “Fundamentals of Biotechnology” of the Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia.
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