Site-directed mutagenesis of Pseudomonas aeruginosa azurin C112D at the M121 position has afforded a series of proteins with elevated Cu-II/I reduction potentials relative to the Cull aquo ion. The high potential and low axial hyperfine splitting (Cu-II electron paramagnetic resonance A(parallel to)) of the C112D/M121L protein are remarkably similar to features normally associated with type 1 copper centers.