Dynamic coordination of two-metal-ions orchestrates λ-exonuclease catalysis.

ABSTRACT: Metal ions at the active site of an enzyme act as cofactors, and their dynamic fluctuations can potentially influence enzyme activity. Here, we use λ-exonuclease as a model enzyme with two Mg²⁺ binding sites and probe activity at various concentrations of magnesium by single-molecule-FRET. We find that while Mg_A²⁺ and Mg_B²⁺ have similar binding constants, the dissociation rate of Mg_A²⁺ is two order of magnitude lower than that of Mg_B²⁺ due to a kinetic-barrier-difference. At physiological Mg²⁺ concentration, the Mg_B²⁺ ion near the 5'-terminal side of the scissile phosphate dissociates each-round of degradation, facilitating a series of DNA cleavages via fast p

SUBMITTER: Hwang W 

PROVIDER: S-EPMC6199318 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature