Details

Autor(en) / Beteiligte

• Ma, Dan
• Lu, Peilong
• Shi, Yigong

Titel

Substrate Selectivity of the Acid-activated Glutamate/γ-Aminobutyric acid (GABA) Antiporter GadC from Escherichia coli

Ist Teil von

• The Journal of biological chemistry, 2013-05, Vol.288 (21), p.15148-15153

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2013

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• GadC, a central component of the Escherichia coli acid resistance system, is a Glu/GABA antiporter. A previous structural study and biochemical characterization showed that GadC exhibits a stringent pH dependence for substrate transport, with no detectable activity at pH values above 6.5. However, the substrate selectivity and the mechanism of pH-dependent transport activity of GadC remain enigmatic. In this study, we demonstrate that GadC selectively transports Glu with no net charge and GABA with a positive charge. A C-plug-truncated variant of GadC (residues 1–470) transported Gln (a mimic of Glu with no net charge), but not Glu, even at pH 8.0. The pH-dependent transport of Gln by this GadC variant was shifted ∼1 unit toward a higher pH compared with Glu transport. Taken together, the results identify the substrate selectivity for GadC and show that the protonation states of substrates are crucial for transport. Background: GadC is a glutamate/GABA antiporter in the Escherichia coli acid resistance system. Results: GadC selectively transports glutamate with no net charge and GABA with a positive charge. C-terminally truncated GadC transports Gln, but not Glu, at pH 7.0 or higher. Conclusion: This study identifies the substrate selectivity for GadC. Significance: The conclusion may be applicable to other members of the APC superfamily.