FIG 5.

The extracellular domain of GluK specifically bound to glutamate. (A) Biolayer interferometry (BLI) analysis of glutamate binding to the extracellular domain of GluK (ecGluK). Glutamine and the extracellular domain of HK AfsQ2 (ecAfsQ2) were used as two negative controls. The concentration of glutamate or glutamine was 20 mM. The concentration of ecGluK or ecAfsQ2 was 2.5 μg/ml. (B) BLI dose-response curves of ecGluK-glutamate interactions. The concentrations of glutamate were 20, 18, 16.2, and 14.6 mM, respectively. (C and D) RT-qPCR analysis of the expression of the gluABCD gene cluster in M145 and the ΔgluR-K mutant on MM supplemented with 10 mM glutamate (C) and 75 mM glutamate (D), respectively. Gene expression is represented as fold change after being normalized to M145.