H-Bonding Maintains the Active Site of Type 1 Copper Proteins: Site-Directed Mutagenesis of Asn38 in Poplar Plastocyanin†

摘要: Type I Cu proteins maintain a trigonal N2S coordination group (with weak axial ligation) in both oxidation states of the Cu2+/+ ion, thereby reducing reorganization energy for electron transfer. Requirements maintaining this were investigated poplar plastocyanin (Pcy) by mutation conserved element type 1 architecture, an asparagine residue (Asn38) adjacent to one ligating histidines. The side chain forms active site clasp via two H-bonds with (Ser85) cysteine (Cys84). In addition, main NH Asn38 donates H-bond thiolate ligand. We have importance these interactions mutating Gln, Thr, and Leu. mutant are capable folding binding Cu2+, but blue color fades; rate fading increases order Gln < Thr is not restored ferricyanide, showing that protein modified irreversibly, probably oxidati...