Spectrochemical studies on the blue copper protein azurin from Alcaligenes denitrificans

Journal Article · Tue Jan 13 04:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00375a011· OSTI ID:6619982

Ainscough, E W; Bingham, A G; Brodie, A M; Ellis, W R; Gray, H B; Loehr, T M; Plowman, J E; Norris, G E; Baker, E N

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 the EPR spectral parameters 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. 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. Measurements of the redox potential, using spectroelectrochemical methods, over the temperature range 4.8-40.0 /sup 0/C, give values for ..delta..H/sup 0/' and ..delta..S/sup 0/' of -55.6 kJ mol/sup -1/ and -97.0 J K/sup -1/ mol/sup -1/, respectively. The redox potential of A. denitrificans azurin at pH 7.0, E/sup 0/, 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. 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.

• Research Organization: Massey Univ., Palmerston North, NZ
• OSTI ID: 6619982
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:1; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
550602 -- Medicine-- External Radiation in Diagnostics-- (1980-)
59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
ABSORPTION SPECTROSCOPY
BACTERIA
COHERENT SCATTERING
COPPER COMPOUNDS
DEUTERIUM COMPOUNDS
DIFFRACTION
ELECTRON SPIN RESONANCE
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
MAGNETIC RESONANCE
METALLOPROTEINS
MICROORGANISMS
ORGANIC COMPOUNDS
PROTEINS
RAMAN SPECTROSCOPY
REDOX POTENTIAL
RESONANCE
SCATTERING
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION