L-homoserine is a non-essential chiral amino acid that plays a very important role in agriculture, the chemical industry, biomedicine, and other fields.In recent years, the production of L-homoserine using microbial fermentation has attracted more and more attention.Amino acid transporters can not only reduce feedback inhibition and cytotoxicity but also increase amino acid production, which have become important targets for metabolic engineering.So far, the L-homoserine transporter in Corynebacterium glutamicum remains unknown.In this study, ten candidate genes involved in L-homoserine transport were selected from Corynebacterium glutamicum through bioinformatics analysis.By L-homoserine tolerance growth experiments in vitro and in vivo, this study found that heterologous overexpression of brnFE, azlCD, and lysE genes could significantly restore the growth defects of the triple homoserine transporter mutant of Escherichia coli strain, however, only deletion of lysE in Corynebacterium glutamicum reduced the biomass by 16% compared with the control, suggesting that the LysE protein showed more important homoserine efflux ability in vivo.Further analysis of the efflux activity of LysE revealed that the efflux ability of the lysE deletion strain was reduced by 18%.Finally, the effect of deletion or overexpression of lysE on L-homoserine production was evaluated in an L-homoserine-producing chassis strain.It was found that deletion of lysE reduced the production of L-homoserine by 65%, while overexpression of lysE increased the production of L-homoserine by 22%.In summary, the LysE protein in Corynebacterium glutamicum exhibited the ability to transport L-homoserine, and the relevant results provide a new target for constructing efficient L-homoserine cell factories.
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