Cell Stress and Chaperones (2012) 17:191–202 DOI 10.1007/s12192-011-0299-x ORIGINAL PAPER Characterisation of the Plasmodium falciparum Hsp70–Hsp90 organising protein (PfHop) Grace W. Gitau & Pradipta Mandal & Gregory L. Blatch & Jude Przyborski & Addmore Shonhai Received: 1 September 2011 / Revised: 3 October 2011 / Accepted: 4 October 2011 / Published online: 18 October 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Malaria is caused by Plasmodium species, whose transmission to vertebrate hosts is facilitated by mosquito vectors. The transition from the cold blooded mosquito vector to the host represents physiological stress to the parasite, and additionally malaria blood stage infection is characterised by intense fever periods. In recent years, it has become clear that heat shock proteins play an essential role during the parasite's life cycle. Plasmodium falciparum expresses two prominent heat shock proteins: heat shock protein 70 (PfHsp70) and heat shock protein 90 (PfHsp90). Both of these proteins have been implicated in the development and pathogenesis of malaria. In eukaryotes, Hsp70 and Hsp90 proteins are functionally linked by an essential adaptor protein known as the Hsp70–Hsp90 organising protein (Hop). In this study, recombinant P. falciparum Hop (PfHop) was heterologously produced in E. G. W. Gitau : A. Shonhai (*) Department of Biochemistry and Microbiology, Zululand University, Kwadlangezwa, South Africa e-mail: ashonhai@pan.uzulu.ac.za A. Shonhai e-mail: adshon@gmail.com P. Mandal : J. Przyborski FB Biology, Philipps University Marburg, 35043 Marburg, Germany G. L. Blatch Biomedical Biotechnology Research Unit, Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown 6140, South Africa G. L. Blatch School of Biomedical and Health Sciences, Victoria University, Melbourne, Victoria 8001, Australia coli and purified by nickel affinity chromatography. Using specific anti-PfHop antisera, the expression and localisation of PfHop in P. falciparum was investigated. PfHop was shown to co-localise with PfHsp70 and PfHsp90 in para- sites at the trophozoite stage. Gel filtration and co- immunoprecipitation experiments suggested that PfHop was present in a complex together with PfHsp70 and PfHsp90. The association of PfHop with both PfHsp70 and PfHsp90 suggests that this protein may mediate the functional interaction between the two chaperones. Keywords Plasmodium falciparum . Molecular chaperone . Hsp70–Hsp90 organising protein . Hsp70 . Hsp90 Abbreviations Hsp70 Hsp90 Hop Hsp40 YT medium IPTG PBS PMSF SDS-PAGE GFP IgG his-tag ATP ADP TCA HRP IP OD Heat shock protein 70 Heat shock protein 90 Hsp70–Hsp90 organising protein Heat shock protein 40 Yeast–tryptophan medium Isopropyl-1-thio-β-D-galactopyranoside Phosphate-buffered saline Phenyl methyl sulfonyl fluoride Sodium dodecyl sulphate-polyacrylamide gel electrophoresis Green fluorescent protein Immunoglobulin G Polyhistidine tag Adenosine triphosphate Adenosine diphosphate Trichloroacetic acid Horseradish peroxidase Immunoprecipitation Optical density