Fluorescence properties of Neurospora tyrosinase

Abstract

Some structural properties of Neurospora tyrosinase have been studied by fluorescence spectroscopy. The emission spectra observed for oxy-, deoxy-, met- and apo-tyrosinase and the Co2+-substituted form are indicative of a protein containing buried tryptophan residues. By using acrylamide and iodide, part of the emission is quenched, indicating heterogeneity in the tryptophan environment. Upon binding of Cu2+ or Co2+ to apo-tyrosinase, a marked decrease of the tryptophan quantum yield is observed. A further decrease in emission intensity results from the binding of molecular O2 to the deoxy form. The fluorescent probe 8-anilinonaphthalene-1-sulphonate binds to tyrosinase only when the metal ions are removed. Reconstitution of apo-tyrosinase with Cu2+ completely displaces the probe, suggesting that 8-anilinonaphthalene-1-sulphonate binds to apo-tyrosinase at the active site. The fluorescence properties of Neurospora tyrosinase are compared with those of haemocyanin.

Roles of Copper Ligands in the Activation and Secretion ofStreptomyces Tyrosinase

“…A similar finding was reported for the tyrosinase of Neurospora, for which an approximately 60% quenching was found upon copper insertion (32). Notably, the complexes from all the mutants except H53Q were similar quenching ranging from 35 to 48% after copper insertion (Fig.…”

Stopped-flow Fluorescence Studies of Inhibitor Binding to Tyrosinase from Streptomyces antibioticus

“…Several Hcs (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39) and one Ty (40) have been the subject of such investigations. Yet Hc or Ty protein fluorescence has never been used to study inhibitor binding.…”

Cloning and Molecular Characterization of a SDS‐Activated Tyrosinase from Marinomonas mediterranea

“…Intrinsic fluorescence can be used to follow changes in protein conformation due to the variations in the environment of aromatic residues. When W residues are surrounding the active site of copper proteins, relevant copper–tryptophan charge transfer interactions can be detected (30), as in the case of Neurospora tyrosinase (20, 31). This technique was used to study the SDS‐activation of broad bean catechol oxidase (16).…”