Figure 8.

sMF6p/FhHDM-1 transfers hemin to apoMYO but not to BSA. A, 20 μm hemin was incubated with 40 μm sMF6p/FhHDM-1 in TBS containing 25 mm caffeine. Both UV/visible absorption spectra prior to (black) and after (red) addition of sMF6p/FhHDM-1 (sFhMF6p) were measured. The sample was then titrated with increasing amounts of apoMYO (0.9, 1.8, 2.6, 3.4, and 4.1 μm final concentrations), and hemin transfer to apoMYO was followed by the increase in the absorbance at 407 nm. The inset shows the UV/visible spectra of MYO prior to hemin extraction (holoMYO) and after hemin reconstitution (MYO). B, another sample of hemin preincubated with sMF6p/FhHDM-1 was titrated with increasing amounts of BSA (10, 20, 30, 38, and 46 μm final concentrations), and the UV/visible absorption spectra were measured. Arrows represent the direction of spectral changes upon addition of apoMYO or BSA. Spectra were not corrected for dilution. AU, absorbance units.