Structure of Pseudomonas aeruginosai zinc azurin mutant Asn47Asp at 2.4 Å resolution

The Pseudomonas aeruginosa azurin mutant Asn47Asp has been isolated, its spectroscopic and kinetic properties characterized, and the X-ray crystal structure of its zinc derivative determined. While the optical and electron paramagnetic resonance spectra as well as the electron-transfer activity of the mutant are very similar to the wild-type values, the Asn47Asp reduction potential is slightly increased by 20 mV. The mutant crystallized in the orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 57.8, b = 81.5 and c = 112.6 A. There are four molecules in the asymmetric unit, packed as a tetramer which consists of two independent dimers. The zinc site of this mutant structure is similar to the wild-type zinc azurin and, in particular, the metal-binding site is almost identical to the site found in the wild-type zinc-azurin structure [Nar, Huber, Messerschmidt, Filippou, Barth, Jaquinod, Kamp & Canters (1992). Eur. J. Biochem. 205, 1123-1129]. The Asp47 side chain at that mutation site takes on a very similar orientation to Asn47 in the wild-type structure preserving the two hydrogen bonds with the neighbouring Thr113 NH and O(gamma)H. Therefore, the increased reduction potential of the mutant is probably a result of an altered charge distribution close to the metal site.

Crystallization and preliminary crystallographic data for the azurin mutant Ala 114 from Pseudomonas aeruginosa

The site-specific mutant alanine 114 of the blue copper protein azurin from Pseudomonas aeruginosa in Escherichia coli has been crystallized from PEG 4000 in a new crystal form compared to the wild type utilizing the hanging-drop procedure. The crystals are blue well-formed prisms. Monoclinic, P2(1), a = 51.03 (5), b = 83.36 (5), c = 66.30 (6) A and beta = 111.0 (1) degrees. 14,875 reflections up to 2.7 A have been collected using a modified Syntex P2(1) automated four-circle diffractometer.