Crystal structure of Pseudomonas aeruginosa apo‐azurin at 1.85 Å resolution
- 20 July 1992
- journal article
- Published by Wiley in FEBS Letters
- Vol. 306 (2-3) , 119-124
- https://doi.org/10.1016/0014-5793(92)80981-l
Abstract
The 3D structure of apo‐azurin from Pseudomonas aeruginosa has been determined at 1.85 Å resolution. The crystal structure is composed of two different molecular forms of apo‐azurin arranged as hetero‐dimers in the tetramer of the asymmetric unit. Form 1 closely resembles the holo‐protein lacking copper. Form 2 shows differences in the metal binding site region induced by the incorporation of a solvent molecule into this site. The positions of the copper ligands His46 and His117 are shifted by 0.6 Å and 1.6 Å. The His117 side chain adopts a position at the surface of the protein, thereby facilitating access to the copper site. The presence of two different molecular forms of apo‐azurin in the crystal lattice may reflect an equilibrium between the two forms in solution. 1H‐NMR spectra or apo‐azurin recorded as a function or pH show that at high pH the line broadening of His35, His46 and His117 resonances is consistent with an interconversion between forms 1 and 2. At low pH, no broadening is observed. This may indicate that here the interconversion is fast on the NMR timescale.Keywords
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