Identification and Characterization of γ-Aminobutyric Acid Uptake System GabP Cg (NCgl0464) in Corynebacterium glutamicum

Abstract

ABSTRACT Corynebacterium glutamicum is widely used for industrial production of various amino acids and vitamins, and there is growing interest in engineering this bacterium for more commercial bioproducts such as γ-aminobutyric acid (GABA). In this study, a C. glutamicum GABA-specific transporter (GabP Cg ) encoded by ncgl0464 was identified and characterized. GabP Cg plays a major role in GABA uptake and is essential to C. glutamicum growing on GABA. GABA uptake by GabP Cg was weakly competed by l -Asn and l -Gln and stimulated by sodium ion (Na + ). The K m and V max values were determined to be 41.1 ± 4.5 μM and 36.8 ± 2.6 nmol min −1 (mg dry weight [DW]) −1 , respectively, at pH 6.5 and 34.2 ± 1.1 μM and 67.3 ± 1.0 nmol min −1 (mg DW) −1 , respectively, at pH 7.5. GabP Cg has 29% amino acid sequence identity to a previously and functionally identified aromatic amino acid transporter (TyrP) of Escherichia coli but low identities to the currently known GABA transporters (17% and 15% to E. coli GabP and Bacillus subtilis GabP, respectively). The mutant RES167 Δ ncgl0464 /pGXKZ9 with the GabP Cg deletion showed 12.5% higher productivity of GABA than RES167/pGXKZ9. It is concluded that GabP Cg represents a new type of GABA transporter and is potentially important for engineering GABA-producing C. glutamicum strains.