2eic
From Proteopedia
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Crystal Structure of Galactose Oxidase mutant W290F
Overview
The function of the stacking tryptophan, W290, a second-coordination, sphere residue in galactose oxidase, has been investigated via, steady-state kinetics measurements, absorption, CD and EPR spectroscopy, and X-ray crystallography of the W290F, W290G, and W290H variants., Enzymatic turnover is significantly slower in the W290 variants. The Km, for d-galactose for W290H is similar to that of the wild type, whereas the, Km is greatly elevated in W290G and W290F, suggesting a role for W290 in, substrate binding and/or positioning via the NH group of the indole ring., Hydrogen bonding between W290 and azide in the wild type-azide crystal, structure are consistent with this function. W290 modulates the properties, and reactivity of the redox-active tyrosine radical; the Y272 tyrosyl, radicals in both the W290G and W290H variants have elevated redox, potentials and are highly unstable compared to the radical in W290F, which, has properties similar to those of the wild-type tyrosyl radical. W290, restricts the accessibility of the Y272 radical site to solvent. Crystal, structures show that Y272 is significantly more solvent exposed in the, W290G variant but that W290F limits solvent access comparable to the, wild-type indole side chain. Spectroscopic studies indicate that the, Cu(II) ground states in the semireduced W290 variants are very similar to, that of the wild-type protein. In addition, the electronic structures of, W290X-azide complexes are also closely similar to the wild-type electronic, structure. Azide binding and azide-mediated proton uptake by Y495 are, perturbed in the variants, indicating that tryptophan also modulates the, function of the catalytic base (Y495) in the wild-type enzyme. Thus, W290, plays multiple critical roles in enzyme catalysis, affecting substrate, binding, the tyrosyl radical redox potential and stability, and the axial, tyrosine function.
About this Structure
2EIC is a Single protein structure of sequence from Gibberella zeae with and as ligands. Active as Galactose oxidase, with EC number 1.1.3.9 Full crystallographic information is available from OCA.
Reference
The Stacking Tryptophan of Galactose Oxidase: A Second-Coordination Sphere Residue that Has Profound Effects on Tyrosyl Radical Behavior and Enzyme Catalysis(,)., Rogers MS, Tyler EM, Akyumani N, Kurtis CR, Spooner RK, Deacon SE, Tamber S, Firbank SJ, Mahmoud K, Knowles PF, Phillips SE, McPherson MJ, Dooley DM, Biochemistry. 2007 Apr 17;46(15):4606-18. Epub 2007 Mar 27. PMID:17385891
Page seeded by OCA on Wed Jan 23 15:34:18 2008
