Copper binding and reactivity at the histidine brace motif: insights from mutational analysis of the <i>Pseudomonas fluorescens</i> copper chaperone CopC

The histidine brace (His-brace) is a copper-binding motif that associated with both oxidative enzymes and proteinaceous copper chaperones. Here, we used biochemical structural methods to characterize mutants of His-brace-containing chaperone from Pseudomonas fluorescens (PfCopC). A total 15 amino acid variants in primary second sphere residues were produced characterised terms their redox properties. PfCopC has very high affinity for Cu(II) also binds Cu(I). reorganisation barrier likely prevents redox-cycling and, thus, catalysis. In contrast, mutations the conserved second-sphere Glu27 enable slow oxidation ascorbate. crystal structure variant E27A confirmed at His-brace. Unexpectedly, Asp83 equatorial position was shown be indispensable binding His-brace PfCopC. mutant designed mimic lytic polysaccharide monooxygenase-like family X325 did not bind Cu(II), but still able These results highlight importance environment around reactivity difference between enzyme chaperone.