Plasmodium falciparum Hsp70–Hsp90 organising protein 195 Fig. 1 Multiple sequence alignment of plasmodial, yeast and mamma- lian Hop homlogues. Multiple sequence alignment of TPR domains of Hop homologues from Pfal (Plasmodium falciparum, PlasmoDB accession number, PF14_0324), Pviv (Plasmodium vivax, NCBI accession number, XP_001616631.1), Pkno (Plasmodium knowlesi, NCBI accession number, XP_002260669.1), Pcha (Plasmodium cha- baudi, NCBI accession number, XP_745506.1), Pber (Plasmodium berghei, NCBI accession number, XP_677465.1), Pyoe (Plasmodium yoelii, NCBI accession number, XP_731105.1), Hsap (Homo sapiens, NCBI accession number, NP_006810.1), Mmus (Mus musculus, NCBI accession number, BC003794.1), and Scer (Saccharomyces cerevisiae, NCBI accession number, CBZ50259.1). TPR domains are highlighted as follows: TPR1 (red solid box), TPR2A (red dashed box) and TPR2B [red dotted box] (Scheufler et al. 2000). Amino acids that are implicated in TPR1–PfHsp70 and TPR2A–PfHsp90-1 interaction are indicated by blue arrows (Scheufler et al. 2000; Odunuga et al. 2003; 2004). Residues constituting DP1 and DP2 repeat (Carrigan et al. 2005) motifs are highlighted by green rectangles analysis (IFA) using anti-PfHop antibodies that we devel- oped (Fig. 4a). The fluorescence signal (red signal) was observed in the cytosol of parasites that had been cultured at 37°C. To further investigate the cellular localisation of PfHop, we created a transgenic parasite line expressing PfHop attached to a C-terminal GFP tag. PfHop-GFP localised largely to the body of the parasite (Fig. 4b). The GFP signal was not detected in the nucleus, suggesting that PfHop may not localise to the nucleus under normal growth conditions. By indirect immunofluorescence, we investigat- ed whether PfHop-GFP co-localises with PfHsp90. It appears that PfHop-GFP and PfHsp90 co-localise in the cytosol and their distribution assumed a uniform pattern in the cell (Fig. 4c). PfHop-GFP and PfHsp70 co-localised in the cytosol; however, they associated less uniformly than PfHop-GFP and PfHsp90 (Fig. 4c, d). The expression of PfHop-GFP by the transfected parasites was confirmed by Western blot analysis (Fig. 4e). As loading control, a Western blot was conducted using antibodies recognising P. falciparum aldolase (Fig. 4e, third panel).