Figure 5. Binding of ATP and ADP to Af-GlnK3.

Contrary to observations made with the homologous Af-GlnK2 the titrations of (A) ATP and (B) ADP in the presence of 25 mM Mg²⁺ do not show signs of cooperative behavior. The integrated heat data (bottom panel) was fit with a model implying identical sites. The resulting enthalpies and dissociation constants underline that ATP is a much stronger ligand than ADP (Table 2).