Open AccessStructural basis of charge transfer complex formation by riboflavin bound to 6,7‐dimethyl‐8‐ribityllumazine synthase
Author(s) -
Koch Michael,
Breithaupt Constanze,
Gerhardt Haase Stefan, Ilka,
Weber Stefan,
Cushman Mark,
Huber Robert,
Bacher Adelbert,
Fischer Markus
Publication year - 2004
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.2004.04253.x
Subject(s) - chemistry , riboflavin , charge (physics) , atp synthase , basis (linear algebra) , biochemistry , enzyme , biophysics , physics , biology , particle physics , mathematics , geometry
The amino acid residue tryptophan 27 of 6,7‐dimethyl‐8‐ribityllumazine synthase of the yeast Schizosaccharomyces pombe was replaced by tyrosine. The structures of the W27Y mutant protein in complex with riboflavin, the substrate analogue 5‐nitroso‐6‐ribitylamino‐2,4(1 H ,3 H )‐pyrimidinedione, and the product analogue 6‐carboxyethyl‐7‐oxo‐8‐ribityllumazine, were determined by X‐ray crystallography at resolutions of 2.7–2.8 Å. Whereas the indole system of W27 forms a coplanar π‐complex with riboflavin, the corresponding phenyl ring in the W27Y mutant establishes only peripheral contact with the heterocyclic ring system of the bound riboflavin. These findings provide an explanation for the absence of the long wavelength shift in optical absorption spectra of riboflavin bound to the mutant enzyme. The structures of the mutants are important tools for the interpretation of the unusual physical properties of riboflavin in complex with lumazine synthase.