Fig. 2.

PfPLSCR undergoes conformational changes in the presence of metal ions. A) SDS-PAGE of the expression and solubilisation of His::PfPLSCR. The purified recombinant protein runs at the predicted molecular weight of ∼ 37 kDa. Pellet and supernatant fractions are labelled as ‘P’ and ‘SN’, respectively. B) BN-PAGE of eluted fractions from the main peak reveals two protein species between the 66 kDa and 146 kDa protein markers (black arrow heads), indicating a possible dimerisation/oligomerisation of His::PfPLSCR. C) Alignment of the putative Ca²⁺ binding regions from different PLSCR1 orthologues. Residues in positions 1, 3, 5, 7, 9 and 12 of the EF-hand-like motif in hPLSCR1 have been proposed to octahedrally coordinate the calcium ion [24] and are shown in bold. Highly conserved residues are highlighted in blue, hydrophobic residues (positions 5 and 7) in green and the strictly conserved phenylalanine residues (position 9) are shown red. D & E) Representative binding curves and calculated affinities (for the shown experiments) of recombinant PfPLSCR for Ca²⁺ and Mg²⁺ ions, respectively. The concentration-dependent decrease of fluorescence at λ 330 nm is plotted as F/F_max with F = fluorescence measured in the presence of cations and F_max= fluorescence under EGTA conditions. A selection of emission spectra is shown in the upper right corner.