Investigation of the Copper Binding Site And the Role of Histidine As a Ligand in Riboflavin Binding Protein

Riboflavin Binding Protein (RBP) binds copper in a 1:1 molar ratio, forming a distinct well-ordered type II site. The nature of this site has been examined using X-ray absorption and pulsed electron paramagnetic resonance (EPR) spectroscopies, revealing a four coordinate oxygen/nitrogen rich environ...

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Bibliographic Details
Published in:Inorganic chemistry 2009-05, Vol.47 (15)
Main Authors: Smith, S.R., Bencze, K.Z., Russ, K.A., Wasiukanis, K., Benore-Parsons, M., Stemmler, T.L.
Format: Article
Language:English
Subjects:
ABSORPTION
BASIC BIOLOGICAL SCIENCES
BOND LENGTHS
COORDINATES
COPPER
CORRELATIONS
DATA
ELECTRON SPIN RESONANCE
ENDOR
ENVIRONMENT
FINE STRUCTURE
HISTIDINE
INCLUSIONS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
LIGANDS
NITROGEN
Other,OTHER, CHEM
OXYGEN
PROTEINS
RIBOFLAVIN
SIMULATION
SPECTROSCOPY
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Summary:Riboflavin Binding Protein (RBP) binds copper in a 1:1 molar ratio, forming a distinct well-ordered type II site. The nature of this site has been examined using X-ray absorption and pulsed electron paramagnetic resonance (EPR) spectroscopies, revealing a four coordinate oxygen/nitrogen rich environment. On the basis of analysis of the Cambridge Structural Database, the average protein bound copper-ligand bond length of 1.96 {angstrom}, obtained by extended x-ray absorption fine structure (EXAFS), is consistent with four coordinate Cu(I) and Cu(II) models that utilize mixed oxygen and nitrogen ligand distributions. These data suggest a Cu-O{sub 3}N coordination state for copper bound to RBP. While pulsed EPR studies including hyperfine sublevel correlation spectroscopy and electron nuclear double resonance show clear spectroscopic evidence for a histidine bound to the copper, inclusion of a histidine in the EXAFS simulation did not lead to any significant improvement in the fit.
ISSN:0020-1669
1520-510X