Figure 4. HPLC analysis of pigments extracted from E. coli strains expressing Synechocystis and Arabidopsis cyclases.

E. coli strains contained (A) IM (chlI-chlD-chlH-gun4-chlM), (B) IA (chlI-chlD-chlH-gun4-chlM-acsF), (C) IM-cycI, (D) IM-cycI-ycf54, (E) IM-CHL27 and (F) IM-CHL27-YCF54 plasmids. Protein expression was induced with IPTG, and ALA and Mg²⁺ were supplemented to boost the production of cyclase substrate, MgPME. Pigments were extracted from the same number of cells except for the strains containing IA and IM-cycI-ycf54 plasmids, for which only 1/10th of cells were used. Elution of cyclase substrate and product was monitored by absorbance at 440 nm. Retention times and spectra (inset) of peaks are used to identify pigment species.