Anti-cooperativity in the two electron oxidation of the S118C disulfide dimer of azurin

Anisotropic spin label mobilities in azurin from 95 GHz electron paramagnetic resonance spectroscopy

“…The X-ray structure of azurin reveals that both K27 and Q12 are residues close to the surface of the protein, but the EPR results show that the spin label attached to Q12 is less mobile than that attached to K27. While S118 is also close to the surface, the reluctance to form disulfide linked dimers suggests that the cysteine in S118C must be buried [9]. This seems consistent with the observation that the spin label is the most immobile for this mutant.…”

“…Site-directed mutagenesis was performed to obtain the K27C and S118C azurin mutants as described previously [9,10]. The preparation of the Q12C azurin mutant will be described elsewhere.…”

The electrochemical characteristics of blue copper protein monolayers on gold

“…We believe that this is related to the relatively limited solvent exposure of the 118C residue and the mild structural deformation that is known to accompany its covalent binding [43]. Significantly, this perturbation is not evident in data acquired from the other protein forms.…”

High-field (275 GHz) spin-label EPR for high-resolution polarity determination in proteins

“…The X-ray structure of azurin [6], reveals that all residues are close to the surface. The difficulty to dimerize S118C-azurin has been interpreted as evidence for a low solvent accessibility of S118 [7]. Also, mobility studies performed by W-band EPR reveal a significantly reduced mobility for S118C [8], suggesting that S118 is more buried than the other residues.…”