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Alpha crystallin domain mutations increase holdase capacity of the archeal small heat shock protein, Tpv HSP 14.3

Kocabıyık, Semra
Zabci, Sema
Protein stability involves the ability of native, folded protein structure to withstand the disruptive, denaturing effects of the external environment. Proteins used in many medical or biotechnological processes are often subjected to conditions which may trigger their degradation, aggregation or inactivation. Therefore, stabilization of proteins is one of the most challenging tasks that has to be addressed in protein based technologies. Many methods have been proposed for improvement of chemical and/or physical instability of proteins. An effective strategy is exploiting the capacity of molecular chaperone sHSPs that act as holdases to bind a wide range of proteins and thereby impede the deleterious effects of their aggregation. This current approach has been promising for various successful applications including proteomics, nanobiotechnology, bioproduction, bioseparation. The focus of our research is the use of an archeal sHSP (Tpv HSP14.3) to enhance thermal stability of a mesophilic enzyme citrate synthase (opt. temp 35°C) as the model substrate. Temperature dependent chaperone activities of the wild type sHSP and its mutant variant TpvHSP14.3 (with ACD mutations) were investigated, comparatively. Thermal stability of the citrate synthase at 47°C was increased significantly by wild type and mutant sHSP as revealed by 9-fold and 11-fold increase in its activity, respectively. Structural analysis showed that increased chaperone activity displayed by the mutant sHSP may be due to local structural change in the β6–β7 zone of ACD resulting in perturbation of oligomer integrity which then impacts protein binding capacity.