FIG. 5.
Heme staining of holocytochrome c4:His6 induced with increasing concentrations of arabinose shows that an N-terminal six-His tag on CcmD reduces its function. E. coli RK103 coexpressing pRGK353 and either pRGK373 (lanes 1 to 7) or pRGK372 (lanes 8 to 14) was grown and treated as described in the text. A typical blot to determine the levels of holocytochrome c4 (indicated at the bottom) compared to 100% (lane 3) is shown. The concentrations of arabinose are indicated above the lanes. The molecular masses of the standards (lane Std) are 29.2 kDa (top band) and 20.2 kDa (bottom band). Abbreviations: ΔCCM, E. coli RK103; SysIΔD, pRGK353; pBADc4-CcmD, pRGK373; pBADc4-6XHis:CcmD, pRGK372; c4, B. pertussis cytochrome c4.