| Abstract | Infrared spectra of the blue copper protein azurin and of apoazurin from P. fluorescens were obtained in aqueous solution. Using resolution enhancement procedures, a number of component bands were identified in the region of the amide I mode, and these bands were assigned to various components of protein secondary structure. A quantitative analysis of these infrared spectra indicates that the secondary structure of P. fluorescens azurin in solution is very similar to those determined previously by X-ray diffraction for the crystals of azurins from other bacterial species. The major components of this structure are β strands and turns. Infrared spectra also evince a remarkable thermal stability of the native azurin. A significant unfolding of the protein could only be detected at temperatures above approximately 76°C. While the secondary structure of apoazurin is practically indistinguishable from that of the native protein at room temperature, the thermal stability of the apo form is significantly reduced. |
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