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Spectroscopic and electrochemical studies, incorporating electronic spectra, electron paramagnetic resonance (EPR) spectra, resonance Raman (RR) spectra, and measurements of the redox potential, have been carried out on the blue copper protein azurin, from Alcaligenes denitrificans. These data are correlated with the refined crystal structure of this azurin and with corresponding data for other blue copper proteins. The electronic spectrum, characterized by an intense (epsilon = 5100 M-1 cm-1) charge-transfer band at 619 nm, the EPR spectral parameters (g perpendicular = 2.059, g parallel of = 2.255, A parallel of = 60 X 10(-4) cm-1), and the resonance Raman spectrum are similar to those obtained from other azurins and from plastocyanins. Both the electronic spectrum and the EPR spectrum are unchanged over the pH range 4-10.5, but major changes occur above pH 12 and below pH 3.5. A small reversible change occurs at pH approximately 11.4. In the RR spectrum the Cu-S stretching mode is shown to contribute to all of the five principal RR peaks. Deuterium substitution produces shifts in at least seven of the peaks; these shifts may be attributable, at least in part, to the NH...S hydrogen bond to the copper-ligated Cys-112. Measurements of the redox potential, using spectroelectrochemical methods, over the temperature range 4.8-40.0 degrees C, give values for delta H0' and delta S0' of -55.6 kJ mol-1 and -97.0 J K-1 mol-1, respectively. The redox potential of A. denitrificans azurin at pH 7.0, Eo', is 276 mV. These data are interpreted in terms of a copper site, in azurin, comprising three strong bonds, in an approximately trigonal plane, from Cys-112, His-46, and His-117 and much longer axial approaches from Met-121 and the peptide carbonyl oxygen of Gly-45. Spectral differences within the azurin family and between azurin and plastocyanin are attributed to differences in the strengths of these axial interactions. Likewise, the distinctly lower Eo values for azurins, as compared with plastocyanins, are related to the more copper(II)-like site in azurin [with a weaker Cu-S(Met) interaction and a Cu-O interaction not found in plastocyanin]. On the other hand, the relative constancy of the EPR parameters between azurin and plastocyanin suggests they are not strongly influenced by weakly interacting axial groups.
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
May 1990,
Gene,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
November 1979,
Journal of molecular biology,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
April 1983,
Journal of molecular biology,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
September 1996,
European journal of biochemistry,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
May 1993,
Acta crystallographica. Section D, Biological crystallography,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
March 1989,
FEBS letters,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
December 1987,
Journal of bacteriology,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
December 2004,
Inorganic chemistry,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
March 1988,
The Journal of biological chemistry,
E W Ainscough, and
A G Bingham, and
A M Brodie, and
W R Ellis, and
H B Gray, and
T M Loehr, and
J E Plowman, and
G E Norris, and
E N Baker
December 1954,
Journal of general microbiology,
