Fig. 3: Heme-induced fluorescence quenching of tryptophan residues in the four variants of TrK13 proteins without profound changes in the circular dichroism profile. | Communications Biology

Fig. 3: Heme-induced fluorescence quenching of tryptophan residues in the four variants of TrK13 proteins without profound changes in the circular dichroism profile.

From: Artemisinin-resistant Plasmodium falciparum Kelch13 mutant proteins display reduced heme-binding affinity and decreased artemisinin activation

Fig. 3

A–D Fluorescence spectra of TrK13-WT (A), TrK13-R539T (B), TrK13-C580Y (C), and TrK13-A578S (D) incubated in the absence (dotted lines) or presence of heme at final concentrations between 0.5-5.0 μM heme (gradual light to dark shading in each color) and showing a successive decrease in fluorescence intensity. E Changes in tryptophan fluorescence quenching in the four variants of TrK13 as deduced from A to D. F Plots of log[(F0-F)/F] versus log[heme] for the interaction of TrK13-WT protein and heme deduced from A to D. The Stern-Volmer quenching constants (KSV), association constants (Ka) and the number of binding sites (n) were calculated from the equations F0/F = Ksv [Q] + 1 and log [(F0-F/F] = logKa + nLog[Q], where F0 = fluorescence intensity in the absence of heme, F = fluorescence intensity in the presence of heme, [Q] = concentration of quencher (heme). Curves are the average of three replicates. G Tabular representation of Ksv, Ka and n.

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