Fig. S1. Morphological features presented by erythrocytes infected with the 3D7 mutant used in this study.

A–C. Transmission electron micrographs showing knobs at the surface of parasitized erythrocytes containing HbAA (A), HbCC (B) and HbSC (C). Sections of high-pressure frozen, freeze substituted cells are shown. Typical examples of knobs are highlighted by arrowheads. Knob density and morphology are known to be aberrant in parasitized erythrocytes containing haemoglobin S or C (Fairhurst et al., 2012), as also shown in these images, but were not further investigated in this study.

D–F. Gallery of representative young Maurer's clefts present in ring-infected erythrocytes. The preservation procedures were as follows: (D) cryo-preservation; (E) high-pressure freezing and freeze-substitution, and post-staining with uranyl acetate revealing a densely packed protein coat on the surface of the Maurer's clefts. (F) High-pressure freezing and freeze-substitution, and stained only with osmium tetroxide to reveal membranes. Occasionally, the two leaflets of the membrane bilayer can be seen both for Maurer's clefts (black arrowheads) and for the erythrocyte plasma membrane (white arrowheads).

Scale bars in (A) to (C), 1 μm; in (D) to (F), 100 nm.

Fig. S2. Frequency histogram showing the speed distributions of Maurer's clefts in trophozoite-infected erythrocytes containing HbAA (white bars) and HbAC (grey bars).

Fig. S3. Simulated Brownian motion of a spherical particle with the radius of a ring-stage Maurer's cleft. The following parameters were entered into the Stokes–Einstein equation: radius, 220 nm; temperature, 37°C; internal viscosity of an erythrocyte, 0.15 Pa·s (Williams and Morris, 1980).

A. Results of 1000 simulations. The speed at which the particle would move is shown.

B. Actual movement of the particle over 40 s.

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