Hexahistidine-tagged human CCHL (with a periplasmic signal) attaches heme to human cytochrome c. Cobalt (Talon) resin purification of IPTG-induced 6xHis:CCHL (pET226xHis:CCHL; pRGK400) expressed in RK112 (BL21(DE3) Δccm). Purification fractions run on SDS-PAGE and detected with (A) Coomassie Blue stain and (B) 6xHis antisera by Western blot. Protein fractions are given above each lane, where lane 2 (L; crude extract load), lane 3 (flow through), lane 4 (wash 1), lane 5 (wash 2), lane 6 (imidazole elution). (C) Heme stain of periplasmic shock proteins from IPTG- and arabinose-induced RK112 containing pRGK400 and pRGK390 (lane 1; labeled SysIII Δccm) or pRGK390 only (lane 2; labeled Δccm). Protein molecular weight standards are shown (labeled M) in lane 1 (A and B; masses on left) and lane 3 (C; masses on right). The position of 6xHis:CCHL and its proteolytic products (A and B) and of holoCycS:6xHis (C) are denoted with arrows.