Reversible active site protonation and electron-transfer properties of Achromobacter cycloclastes pseudoazurin: comparisons with other type 1 copper proteins

Abstract

Kinetic and NMR studies on the copper(I) form of A. cycloclasters pseudoazurin provide evidence for an active site protonation (and dissociation) equilibrium process involving His81, pK_a 4.9 (average); the three type 1 copper proteins now known to exhibit this behaviour have just two amino acids separating the ligating Cys and His residues in the C-terminal region.