Conformational heterogeneity of the copper binding site in azurin : A time-resolved fluorescence study

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TypeArticle
Journal titleBiophysical Journal
Volume41
Issue3
Pages233244; # of pages: 12
AbstractComparison of the fluorescence spectra and the effect of temperature on the quantum yields of fluorescence of Azurin (from Pseudomonas fluorescens ATCC-13525-2) and 3-methylindole (in methylcyclohexane solution) provides substantive evidence that the tryptophan residue in azurin is completely inaccessible to solvent molecules. The quantum yields of azurin (CuII), azurin (CuI), and apoazurin (λex = 291 nm) were 0.052, 0.054, and 0.31, respectively. Other evidence indicates that there is no energy transfer from tyrosine to tryptophan in any of these proteins. The fluorescence decay behavior of each of the azurin samples was found to be invariant with emission wavelength. The fluorescences of azurin (CuII) and azurin (CuI) decay with dual exponential kinetics (τ₁ = 4.80 ns, τ₂ = 0.18 ns) while that of apoazurin obeys single exponential decay kinetics (τ = 4.90). The ratio of pre-exponentials of azurin (CuII), α₁/α₂, is found to be 0.25, and this ratio increases to 0.36 on reduction to azurin (CuI). The results are interpreted as originating from different interactions of the tryptophan with two conformers of the copper-ligand complex in azurin.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Institute for Biological Sciences
Peer reviewedNo
NRC numberSZABO1983
NPARC number12327428
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Record identifierfe8349bf-2ddc-4ca5-b44b-6ff6839ccabc
Record created2009-09-10
Record modified2016-05-09
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