FIG. 5.

Heme staining of holocytochrome c₄:6×His with increasing concentrations of ZnPPIX. E. coli RK105 cultures containing pRGK333, pRGK332, and pHPEX2 were grown in the presence of 8 μM heme (lanes 1 and 3 to 5) or 25 μM heme (lane 2) to an OD₆₀₀ of approximately 0.5. ZnPPIX was added (lanes 3 to 5), and 1 mM IPTG was added to induce synthesis of the system I proteins. The cultures were incubated for 1 h, and 0.2% arabinose was added for 3 h to induce the synthesis of cytochrome c₄. The concentrations (in μM) of heme and ZnPPIX are indicated above the lanes. SysI, pRGK333; c₄:6×His, pRGK332; cyt c₄, cytochrome c₄.