FIG 3 .

GlnH bound diverse amino acids, with highest affinity for Asp. (A) The melting temperatures of GlnH were 47°C in the absence of amino acids (solid line) and 59°C in the presence of 10 mM aspartate (dashed line). (B) Asp, Glu, Asn, His, and Cys significantly stabilized GlnH (increase in melting temperature of >2°C; P < 0.05), whereas other amino acids did not. (C) Binding of Asp to GlnH was measured by isothermal calorimetry (ITC). (D) The melting temperatures of C. glutamicum GlnH were 24°C in the absence of amino acids and 39 or 34°C in the presence of 10 mM Asp or Glu, respectively. (E) Binding of Asp to C. glutamicum GlnH was measured by changes in the intrinsic tryptophan fluorescence. Error bars represent standard deviations from at least three measurements. Graphs are representative of three independent experiments.