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 environment. On the basis of analysis of the Cambridge Structural Database, the average protein bound copper-ligand bond length of 1.96 A, 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 3N 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.
Smith
Sheila R
SR
Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48101, USA. sheilars@umd.umich.edu
Bencze
Krisztina Z
KZ
Russ
Kristen A
KA
Wasiukanis
Kristen
K
Benore-Parsons
Marilee
M
Stemmler
Timothy L
TL
D015502:Absorptiometry, Photon; D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006639:Histidine / Q000378:metabolism*; D008024:Ligands; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*
D008024:Ligands; D026901:Membrane Transport Proteins; C019079:riboflavin-binding protein; D006639:Histidine; D003300:Copper