Allosteric Mechanism in Chorismate Mutase
Chorismate mutase (CM) is a metabolic enzyme in the amino acid biosynthesis pathway that exhibits all the hallmarks of allostery. Yet, despite its larger size (60 kDa), it is amenable to detailed study by NMR. CM has a homodimeric structure that has been shown to adopt distinct, classical ‘tense’ (T) and ‘relaxed’ (R) quaternary conformations. CM reactivity is intrinsically positively cooperative, even though the two symmetric active sites are at opposite sites of the dimer, and CM can be both positively and negatively modulated by the allosteric effector ligands tryptophan and tyrosine. Application of NMR spectroscopy to this rich system should enable discovery of structural and dynamic processes that underlie classical allosteric regulation. In particular, we are interested in how the binding event in one protomer can extend to the other protomer active site – via conformational change or other dynamic processes – to stimulate higher activity.