Characterisation of a unique linker segment of the Plasmodium falciparum cytosol localised Hsp110 chaperone

Publication year: 2021
Authors: G. Chakafana a,b, P.T.Mudau a, T.Zininga a,c, A.Shonhai a

a - Department of Biochemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa
b - Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
c - Department of Biochemistry, Stellenbosch University, Stellenbosch 7600, South Africa

Published in: International Journal of Biological Macromolecules, 2021, Vol.180, p. 272-285
doi: 10.1016/j.ijbiomac.2021.03.056

Plasmodium falciparum expresses two essential cytosol localised chaperones; PfHsp70-1 and PfHsp70-z. PfHsp70-z (Hsp110 homologue) is thought to facilitate nucleotide exchange function of PfHsp70-1. PfHsp70-1 is a refoldase, while PfHsp70-z is restricted to holdase chaperone function. The structural features delineating functional specialisation of these chaperones remain unknown. Notably, PfHsp70-z possesses a unique linker segment which could account for its distinct functions. Using recombinant forms of PfHsp70-1, PfHsp70-z and E. coli Hsp70 (DnaK) as well as their linker switch mutant forms, we explored the effects of the linker mutations by conducting several assays such as circular dichroism, intrinsic and extrinsic fluorescence coupled to biochemical and in cellular analyses. Our findings demonstrate that the linker of PfHsp70-z modulates global conformation of the chaperone, regulating several functions such as client protein binding, chaperone- and ATPase activities. In addition, as opposed to the flexible linker of PfHsp70-1, the PfHsp70-z linker is rigid, thus regulating its notable thermal stability, making it an effective stress buffer. Our findings suggest a crucial role for the linker in streamlining the functions of these two chaperones. The findings further explain how these distinct chaperones cooperate to ensure survival of P. falciparum particularly under the stressful human host environment.

MP-SPR keywords: binding, CMD 3D, CMD sensor slide, protein-protein interaction