Structural and functional studies on a small Heat Shock Protein from Entamoeba histolytica

Abstract

Small Heat Shock Proteins (sHSPs) are molecular chaperones that bind to unfolding proteins during cellular stress to prevent them from aggregation. Once the normal conditions are restored, sHSPs release the bound substrate proteins to appropriate cellular machinery either for degradation or for further folding to attain their functional forms. Due to this property of sHSPs to prevent the aggregation of non-native proteins which helps in maintaining proteostasis, they are implicated in several diseases involving defective protein folding. sHSPs are present is all kingdoms of life. Functional characterization of several mammalian, plant and bacterial sHSPs have been reported whereas the structural information is limited. In solution, sHSPs are known to exist as a heterogeneous mixture of a variety of oligomers in a dynamic equilibrium involving constant exchange of subunits. Crystal structures of a few of the higher oligomers as cage-like closed particles have been reported. Studies on protozoan sHSPs are limited. The roles of only a few protozoan sHSPs in infection, survival and migration in the host have been reported so far and no structural information is available. Here we present the structural and functional studies that we carried out on a sHSP (HSP18.5) from the protozoan Entamoeba histolytica. newline