Fig. 4
From: Sustainable and high-level microbial production of plant hemoglobin in Corynebacterium glutamicum
Combinatorial optimization of multiple elements for enhancing hemoglobin expression. A Schematic diagram of combination of PprpD2 promoter variants with hemoglobin NCS variants. B Effects of combination of PprpD2 promoter variants with hemoglobin NCS variants on hemoglobin expression. C Effects of plasmid copy number modification on hemoglobin expression. D Analysis of intracellular hemoglobin expression by SDS–PAGE. M, protein marker. 1, empty plasmid control. 2, Lba-Ec with unoptimized NCS and the wild-type PprpD2 promoter. 3, Lba-Ec with the optimized NCS variant (N1) and the wild-type PprpD2 promoter. 4, Lba-Ec with the unoptimized NCS and the optimized PprpD2 promoter variant (P6). 5, Lba-Ec with the optimized NCS variant (N1) and the optimized PprpD2 promoter variant (P6). 6, Lba-Ec with the optimized NCS variant (N1) and the optimized PprpD2 promoter variant (P6) in a high-copy plasmid (copA1 mutation, 107 copies). E Effects of hemoglobin expression on cell growth. The C. glutamicum strain with an empty plasmid was used as the control. The hemoglobin expression levels were characterized by measuring the fluorescence intensities of hemoglobin–GFP fusion. Values and error bars represent means and standard deviations (n = 3)