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In order to engineer unnatural fusion proteins for heterologous production of the plant polyphenolic compound resveratrol,two short peptide linkers of various length were fused between Arabidopsis thaliana 4-coumarate:coenzyme A ligase(4CL)and Polygonum cuspidatum stilbene synthase(STS)to generate fusion proteins 4CL-(GSG)n-STS(n ≤5)and 4CL-(GGGGS)n-STS(n ≤4).The fusion proteins were expressed in both Escherichia coli and Saccharomyces cerevisiae,and resveratrol production was tested in vitro and in vivo using purified enzymes and the engineered strains,respectively.The catalytic efficiency of the fusions decreased gradually with increasing number of GSG or GGGGS repeats in the linker.In the yeast system in vivo,resveratrol production by the strain expressing 4CL-(GSG)1-STS was 2.3-fold greater than the strain expressing 4CL-(GSG)5-STS,while expression of 4CL-(GGGGS)1-STS resulted in 1.6-fold higher resveratrol than 4CL-(GGGGS)4-STS.Similarly,in the E.coli system,expression of 4CL-(GSG)1-STS and 4CL-(GGGGS)1-STS increased resveratrol production by 2.1-fold and 1.7-fold compared with 4CL-(GSG)5-STS and 4CL-(GGGGS)4-STS,respectively.E.coli appeared to be superior for resveratrol biosynthesis since the average yield was 3-fold higher than S.cerevisiae.In conclusion,this work demonstrates that both linker type and length influence the catalytic efficiency of fusion proteins for resveratrol biosynthesis,and(GSG)1 proved to be the best linker between 4CL and STS.