Systems metabolic engineering of Escherichia coli for the bioproduction of biliverdin and phycoerythrobilin

Abstract

Phycobiliprotein is an important co-pigment in photosynthesis, which is composed of the covalent combination of apoprotein and phycobilin. Biliverdin IXα and phycoerythrobilin are both important substances in the phycobiliprotein biosynthesis pathway. As an economic red seaweed, Neoporphyra haitanensis has a high content of phycoerythrin. Therefore, in this study, we explored new enzyme resources for the heterologous biosynthesis of biliverdin and phycoerythrobilin. Specifically, we identified and isolated the genes encoding NhHO1, NhPebA and NhPebB from N. haitanensis, which are integral components of its phycoerythrin biosynthetic pathway. Additionally, ApHO1 from Arthrospira platensis and PebS from Prochlorococcus phage P-SSM2 were selected for comparative analysis. The results showed that genes from N. haitanensis did not encode active enzymes, which might be ascribed to the absence of crucial motifs. However, the transformation of ApHO1 and PebS into Escherichia coli could lead to the synthesis of biliverdin and phycoerythrobilin. This is the first report of sequence analysis and enzyme activity verification of phycoerythrin synthesis genes from N. haitanensis, providing a foundation for future explorations into its potential genetic resources. The successful production of biliverdin and phycoerythrobilin lay a foundation for the environmentally friendly preparation of phycobiliprotein.

Keywords: biliverdin; biosynthesis; heterologous expression; neoporphyra haitanensis; phycoerythrobilin.

Figure 1

Phylogenetic relationship, motifs and conserved domains of the HO proteins. (a) Phylogenetic tree constructed based on HO protein sequences. The tree was constructed using the Neighbor-Joining algorithm with 1,000 bootstrap replicates. The bootstrap value is shown at each node. (b) Phylogenetic relationship, motifs (Ten putative motifs were indicated by boxes of different color.) and conserved domains of the HO proteins.

Figure 2

Western blot results of recombinant NhHO1, ApHO1, NhPebA, NhPebB and PebS. (a) Western blot results of recombinant NhHO1, ApHO1 and NhPebA. M: protein ladder, Lane 1: crude enzyme extracted from E. coli BL21 (petDuet-I), Lane 2: crude enzyme extracted from E. coli BL21 (pED-NhHO1), Lane 3 and 4: crude enzyme extracted from E. coli BL21 (pED-ApHO1), Lane 5: crude enzyme extracted from E. coli BL21 (pED-ApHO1 & pRD-NhPebA-NhPebB), Lane 6: crude enzyme extracted from E. coli BL21 (pED-ApHO1-PebS). (b) Western blot results of recombinant NhPebB and PebS. M: protein ladder, Lane 1: crude enzyme extracted from E. coli BL21 (pED-ApHO1), Lane 2: crude enzyme extracted from E. coli BL21 (pED-ApHO1 & pRD-NhPebA-NhPebB), Lane 3: crude enzyme extracted from E. coli BL21 (pED-ApHO1-PebS). Original Western blot results are shown in the Supplementary Figure S2 .

Figure 3

The liquid chromatography-mass spectrometry chromatograms. (a) The extracted ion chromatogram. NhH (pED-NhHO1) and APH (pED-ApHO1) were taken as the experimental group (purple and blue curves), and PET (pETDuet-1) was taken as the control group (red curves). (b) The mass spectrum. Note the molecular ion species formed: [M + H]⁺.

Figure 4

The liquid chromatography-mass spectrometry chromatograms. (a) The extracted ion chromatogram. ApH-AB (pED-ApHO1 & pRD-NhPebA-NhPebB, purple curve) and APH-S (pED-ApHO1-PebS, blue curve) were taken as the experimental groups, and ApH (pED-ApHO1) was taken as the control group (red curves). (b) The mass spectrum. Note the molecular ion species formed: [M + H]⁺.