Role of Ligand-Binding and Non-Active Site Residues in the Dynamics, Conformational Integrity, and Catalysis of the Disordered Enzyme Monomeric Chorismate Mutase

Abstract

The dominant view in enzymology is that an increase in structural disorderedness tends to decrease catalytic efficiency. Surprisingly, engineered monomeric chorismate mutase (mCM), an enzyme with properties of molten globule (intrinsically disordered), efficiently catalyses the conversion of chorismate to prephenate. Therefore, here, we investigate the underlying structural plasticity mechanisms that facilitate this catalysis. We generated rationally designed mutations of mCM and used a battery of spectroscopic tests including Forster resonance energy transfer (FRET) and time-resolved fluorescence anisotropy measurements to probe what influences catalysis. We found that the integrity of the secondary structure, and ligand-induced global compaction (disorder-to-order transition) play a crucial role in catalysis. Intriguingly, we find that even minor perturbation in regions distant from the active site can significantly impact the enzyme efficiency by changing the conformation, segmental dynamics, ligand-induced global compaction, and stability.