Temperature dependence of the resonance Raman spectra of plastocyanin and azurin between cryogenic and ambient conditions.

Abstract

Resonance Raman spectra of spinach plastocyanin and Pseudomonas aeruginosa azurin were studied as a function of temperature between 10 K and 300 K. The spectra are markedly improved both in signal/noise ratio and in resolution at low temperatures. The assignments of the resonance Raman-active vibrations are reinterpreted in view of the number and intensities of peaks observed in the low-temperature spectra. Features appear in the low-temperature spectra of azurin that may be due to copper-bound methionine. The plastocyanin spectra undergo a transition between 220 K and the melting point of water that results in dramatically narrowed peaks at lower temperature and a shift in the carbon-sulfur stretching frequency of the copper-bound cysteine, suggesting a structural change in the active site and an accompanying effect on vibrational dephasing. Considering that the structures and nonvibrational spectroscopies of these two proteins are similar, the substantial differences in the resonance Raman spectra are striking and significant.

Low temperature optical spectroscopy of cobalt-substituted hemocyanin from Carcinus maenas

“…In the resonance Raman spectra of blue copper proteins (Ferris et al 1979;Nestor et al 1984;Woodruff et al 1984) several peaks are found at 140-160 cm-~ and are attributed to ligand-metal-ligand deformation modes (Woodruff et al 1984). In view of this finding we propose that band A should be assigned to an electronic transition having substantial admixture with a rCrqH~ ~ dco transition.…”

Displacement-Parameter Weighted Coordinate Comparison: I. Detection of Significant Structural Differences Between Oxidation States

“…Upon cooling, the cell volume of the plastocyanin crystals decreases by 4.2% (Fields et al, 1994). There is independent evidence that the dynamical properties of plastocyanin change upon lowering the temperature: a discontinuity of the linewidth and background intensity of the resonance Raman signal associated with Cu--S of the cysteine ligand in french bean plastocyanin has been observed between 220 and 260 K (Woodruff, Norton, Swanson & Fry, 1984). Our observation that the regions not involved in cell contacts that have significant differences upon cooling, reduction at pH 3.8, or upon removal of the copper, are the same, suggests that the origin of all the differences is most likely dynamical and 'that the flexibility of the loops is affected both by crystal packing and the presence and oxidation state of the copper.…”

Accuracy and precision in protein crystal structure analysis: two independent refinements of the structure of poplar plastocyanin at 173 K

“…The present work was undertaken largely to test a hypothesis based on resonance Raman experiments that the Cu-site geometry in plastocyanin changes significantly when the protein is cooled to below -273 K (Woodruff, Norton, Swanson & Fry, 1984;Blair et al, 1985). Three changes in the Cu-site geometry were proposed: (i) a decrease in the Cu--S(Met92) bond length, (ii) a consequential inhibition of large-amplitude vibrations of the Cu atom perpendicular to the N2S(Cys) plane, and (iii) a change in the Cu--Sr(Cys84)--Ct~---C '~ dihedral angle.…”

“…A plausible interpretation of this assignment was that the long Cu--S(Met92) bond (2.9 A), which does not contribute to the EXAFS at ambient temperature (Scott et al, 1982), is replaced by a bond about 2.4 A long at low temperature (Penner-Hahn & Hodgson, 1986). Second, it was reported that changes in the resonance Raman (rR) spectrum of plastocyanin close to the freezing point of water can be attributed to a change in the Cu--S~'(Cys84)--Ct~---C'~ dihedral angle, 'the formation of a weak but significant Cu--S(Met92) bond', and the resulting inhibition of 'large-amplitude motions of the Cu atom perpendicular to the NzS(Cys) plane, which are permitted at room temperature due to the virtual absence of a Cu--S(Met) bond' (Woodruff, Norton, Swanson & Fry, 1984;Blair et al, 1985). The putative short Cu--S(Met92) bond deduced from the EXAFS was subsequently shown to be an artefact caused by noise in the data (Penner-Hahn, Murata, Hodgson & Freeman, 1989), but the hypotheses derived from the rR measurements remained to be tested.…”

“…The 'blue' copper protein plastocyanin has been well characterized by crystallographic structure analysis Gewirth, Cohen, Schugar & Solomon, 1987), vibrational spectoscopy (Woodruff, Norton, Swanson & Fry, 1984;Blair et al, 1985;Han et al, 1991), X-ray absorption spectroscopy (Scott, Hahn, Doniach, Freeman & Hodgson, 1982;Penner-Hahn, Murata, Hodgson & Freeman, 1989;Murphy, Hasnain, Strange, Harvey & Ingledew, 1990), elecrochemistry (Bfichi, Bond, Codd, Huq & Freeman, 1992) and kinetic measurements (Jackman, McGinnis, Powls, Salmon & Sykes, 1988;Kyritsis et al, 1991). A quantum-mechanical treatment of the 'blue' copper site is available (Gewirth & Solomon, 1988).…”