Figure 4.

Heme content of purified variant CBS proteins. Photographs of cuvettes containing equal concentrations of each purified protein are shown on the left. (A) Absorption spectra demonstrating the level of heme incorporation for seven CBS proteins. Bacterial cells expressing the various CBS proteins were supplemented with 0.3 mM δ-ALA in the growth medium. (B) Increased incorporation of heme for the CBS variants when expressed with an increased concentration of exogenous δ-ALA in the growth medium (0.3 mM [solid symbols] vs. 0.6 mM [open symbols]).