title: YjeH Is a Novel Exporter of l-Methionine and Branched-Chain Amino Acids in Escherichia coli.
abstract: Amino acid efflux transport systems have important physiological functions and play vital roles in the fermentative production of amino acids. However, no methionine exporter has yet been identified in Escherichia coli. In this study, we identified a novel amino acid exporter, YjeH, in E. coli. The yjeH overexpression strain exhibited high tolerance to the structural analogues of l-methionine and branched-chain amino acids, decreased intracellular amino acid levels, and enhanced export rates in the presence of a Met-Met, Leu-Leu, Ile-Ile, or Val-Val dipeptide, suggesting that YjeH functions as an exporter of l-methionine and the three branched-chain amino acids. The export of the four amino acids in the yjeH overexpression strain was competitively inhibited in relation to each other. The expression of yjeH was strongly induced by increasing cytoplasmic concentrations of substrate amino acids. Green fluorescent protein (GFP)-tagged YjeH was visualized by total internal reflection fluorescence microscopy to confirm the plasma membrane localization of YjeH. Phylogenetic analysis of transporters indicated that YjeH belongs to the amino acid efflux family of the amino acid/polyamine/organocation (APC) superfamily. Structural modeling revealed that YjeH has the typical "5 + 5" transmembrane α-helical segment (TMS) inverted-repeat fold of APC superfamily transporters, and its binding sites are strictly conserved. The enhanced capacity of l-methionine export by the overexpression of yjeH in an l-methionine-producing strain resulted in a 70% improvement in titer. This study supplements the transporter classification and provides a substantial basis for the application of the methionine exporter in metabolic engineering.
authors: School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors: Qian
authors: Q
authors: Liu
authors: CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors: Yong
authors: Y
authors: Liang
authors: CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors: Yun
authors: Y
authors: Zhang
authors: CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors: Xiuling
authors: X
authors: Shang
authors: CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors: Shuwen
authors: S
authors: Liu
authors: CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China.
authors: Jifu
authors: J
authors: Wen
authors: School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China wenty@im.ac.cn.
authors: Tingyi
authors: http://orcid.org/0000-0003-2583-7088
authors: T
authors: Wen
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics* / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008715:Methionine / Q000378:metabolism*
chemical_list: D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000597:Amino Acids, Branched-Chain; D029968:Escherichia coli Proteins; C000609463:YjeH protein, E coli; D008715:Methionine