Cold Adaptation in an Enzyme Can Be Driven by Dynamic Allostery

Abstract

The ability of organisms to diverge and adapt to different environmental niches is a hallmark of evolution, and one of the most prevalent examples is that of thermal adaptation, where two similar organisms can evolve to survive at different extremes of temperature. Underlying the physiological differences between such organisms are changes in the enzymes that catalyze the various reactions, and these changes are often located at surface-exposed amino acids distant from the active site. How such changes mediate the observed differences is activity is not clear. Here we examine surface-exposed GLY mutations to LID and AMPbd domains of E. Coli. adenylate kinase (AK), two domains that are purported to be responsible for mediating enzyme turnover. We show using advanced NMR techniques as well a both isothermal titration (ITC) and differential scanning calorimetry (DSC) that Km (or substrate affinity for ligand), and kcat can be independently and rationally tuned, by making specific surface-exposed mutations in different regions of the molecule. These studies provide insight into how enzymes can evolve to utilize local fluctuations to control catalysis and how evolution can precisely and independently tune these parameters.