Probing the Effect of LPMO "Gatekeeper" Residue Identity on Cu Site Stabilization via Cu K-edge X-ray Absorption Spectroscopy

We have prepared four variants of the NcAA9C LPMO copper enzyme: the wild-type and three mutants in which the gatekeeper residue Glutamine (Gln) has been substituted for Glutamate (Glu), Asparagine (Asn), or Aspartate (Asp). We wish to utilize Cu K-edge and EXAFS data to supplement interpretation and reconciliation of electrochemical, biochemical, EPR, and computational data which we have collected to evaluate the effect of gatekeeper residue identity on the stabilization of the Cu site in the +2 vs +1 oxidation states.