title: Effect of multidrug-efflux transporter genes on dipeptide resistance and overproduction in Escherichia coli.
abstract: L-Alanyl-L-glutamine (Ala-Gln) is a clinically and nutritionally important dipeptide. We have already shown a novel method for the fermentative production of Ala-Gln using an Escherichia coli strain expressing L-amino acid alpha-ligase (Lal), which catalyzes the formation of dipeptides by combining two amino acids. In the course of Ala-Gln-producing strain development, it was revealed that Lal expression caused growth inhibition. We also found that the addition of some dipeptides, including Ala-Gln, inhibited the growth of a multiple peptidase-deficient strain. To further increase the productivity by overcoming the inhibitory effect of dipeptides, we focused on dipeptide transport systems. The four genes (bcr, norE, ydeE and yeeO) were selected from 34 genes encoding a multidrug-efflux transporter of E. coli as those conferring resistance to growth inhibitory dipeptides. Intracellular concentration of Ala-Gln was reduced by overexpressing these genes in a multiple peptidase-deficient strain. Furthermore, overexpression of each gene in the dipeptide-producing strains resulted in the increase of Ala-Gln and L-alanyl-L-branched chain amino acids titers. These results indicate that some multidrug-efflux transporters of E. coli can transport dipeptides and that enhancement of their activities is effective for fermentative production of dipeptides.
authors.affiliation: Bioprocess Development Center, Kyowa Hakko Bio Co. Ltd, Ibaraki, Japan. mikiro.hayashi@kyowa-kirin.co.jp
authors.forename: Mikiro
authors.initials: M
authors.lastname: Hayashi
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tabata
authors.forename: Makoto
authors.initials: M
authors.lastname: Yagasaki
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yonetani
mesh_terms: D001692:Biological Transport; D003470:Culture Media; D004151:Dipeptides / Q000096:biosynthesis / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008025:Ligases / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004151:Dipeptides; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D008025:Ligases; C054122:alanylglutamine