Details

Autor(en) / Beteiligte

• de Jongh, Thyra E.
• Hoffmann, Maren
• Einsle, Oliver
• Cavazzini, Davide
• Rossi, Gian-Luigi
• Ubbink, Marcellus
• Canters, Gerard W.

Titel

Inter- and Intramolecular Electron Transfer in Modified Azurin Dimers

Ist Teil von

• European Journal of Inorganic Chemistry, 2007-06, Vol.2007 (18), p.2627-2634

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2007

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• A dimer of N42C azurin (P. aeruginosa), formed by intermolecular disulfide bond formation between the introduced surface‐exposed cysteine residues, was previously shown to exhibit low rates of intramolecular electron self‐exchange. The work presented here aims to render the construct sensitive to pH by the introduction of an additional surface mutation (M64E). The structural and mechanistic effects of ionisable residues in the hydrophobic patch were analysed as a function of pH. A crystal structure of the dimer at pH = 3.1, solved to 2.3 Å resolution, displays an orientation distinct from other known azurin complexes. The dimer exhibits slow intramolecular self‐exchange at pH* = 4.5 (keseintra ≈ 25 s–1), in line with the Cu–Cu distance of 20.5 Å observed in the crystal structure of the dimer. The intermolecular electron self‐exchange rate constant amounts to kinter = (1.8 ± 0.1) ×104 M–1 s–1. Thus, at protein concentrations less than 1 mm, the intramolecular process dominates the electron self‐exchange. A change from low to high pH results in a slowing down of the electron‐exchange processes. A partitioning between intra‐ and intermolecular exchange proved impossible at low pH due to the limited precision of the experimental data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)