Biophysical analysis of Plasmodium falciparum Hsp70-Hsp90 organising protein (PfHop) reveals a monomer that is characterised by folded segments connected by flexible linkers.

Stanley Makumire,Inari Kursula,Tawanda Zininga,Addmore Shonhai,Juha Vahokoski,Didier Picard

doi:10.1371/journal.pone.0226657

Abstract

Plasmodium falciparum causes the most lethal form of malaria. The cooperation of heat shock protein (Hsp) 70 and 90 is thought to facilitate folding of select group of cellular proteins that are crucial for cyto-protection and development of the parasites. Hsp70 and Hsp90 are brought into a functional complex that allows substrate exchange by stress inducible protein 1 (STI1), also known as Hsp70-Hsp90 organising protein (Hop). P. falciparum Hop (PfHop) co-localises and occurs in complex with the parasite cytosolic chaperones, PfHsp70-1 and PfHsp90. Here, we characterised the structure of recombinant PfHop using synchrotron radiation circular dichroism (SRCD) and small-angle X-ray scattering. Structurally, PfHop is a monomeric, elongated but folded protein, in agreement with its predicted TPR domain structure. Using SRCD, we established that PfHop is unstable at temperatures higher than 40°C. This suggests that PfHop is less stable at elevated temperatures compared to its functional partner, PfHsp70-1, that is reportedly stable at temperatures as high as 80°C. These findings contribute towards our understanding of the role of the Hop-mediated functional partnership between Hsp70 and Hsp90.

Highlights

Heat shock proteins (Hsp) serve primarily as protein folding facilitators
We characterised the structure of recombinant P. falciparum Hop (PfHop) using synchrotron radiation circular dichroism (SRCD) and small-angle X-ray scattering
PfHop is thought to facilitate the functional cooperation between PfHsp70-1 and PfHsp90, both prominent cytosolic molecular chaperones of P. falciparum [18, 19]

Summary

Introduction

Heat shock proteins (Hsp) serve primarily as protein folding facilitators They participate in several other processes, such as protein transport, assembly/disassembly of protein complexes, protein degradation, amongst others [1]. It has been reported that the cytosolic P. falciparum heat shock protein 70–1 (PfHsp70-1) is cyto-protective due to its ability to suppress protein mis-folding and aggregation under stressful conditions [5, 6].

Methods

Results

Conclusion