Toggle Main Menu Toggle Search

Open Access padlockePrints

Effect of histidine 6 protonation on the active site structure and electron-transfer capabilities of pseudoazurin from Achromobacter cycloclastes

Lookup NU author(s): Dr Katsuko Sato, Professor Christopher Dennison


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


The paramagnetic 1H NMR spectrum of Cu(II) pseudoazurin [PACu(II)] contains eight, directly observed hyperfine-shifted resonances which we have assigned using saturation transter experiments on a 1:1 mixture of PACu(I) and PACu(II). The spectrum exhibits a number of similarities to those of other cupredoxins, but differences are found concerning the Cu-S(Met)interaction. The spectrum is dependent on pH* in the range 8.5-4.5 (pKa* 6.4), and a conformational change involving movement of the copper ion away from the Met toward the equatorial ligands, as a consequence of protonation of the surface His6 residue, is identified. Corresponding changes are also seen in the UV/vis spectrum. The protonation/deprotonation equilibrium of His6 influences the reduction potential of the protein in the same pH range. The self-exchange rate constant of PACu at pH* 6.0 (25°C) is considerably smaller (1.1 × 103 M-1 s-1) than the value obtained at pH* 7.6 (3.7 × 103 M-1 s-1). The effect on the self-exchange reactivity is mainly due to an alteration in the reorganization energy of the copper site brought about by the structural change resulting from His6 protonation.

Publication metadata

Author(s): Sato K; Dennison C

Publication type: Article

Publication status: Published

Journal: Biochemistry

Year: 2002

Volume: 41

Issue: 1

Pages: 120-130

ISSN (print): 0006-2960

ISSN (electronic): 1520-4995

Publisher: American Chemical Society


DOI: 10.1021/bi0117448

PubMed id: 11772009


Altmetrics provided by Altmetric