1H NMR characterization of Chromatium gracile high-potential iron protein and its ruthenium-modified derivatives. Modulation of the reduction potentials in low- and high-potential [Fe4S4] ferredoxins.
The NMR spectra of the high-potential iron protein from the photosynthetic bacterium Chromatium gracile and its ruthenium-labeled (His-42 and His-20) derivatives are reported. The isotropically shifted resonances in both the oxidized and reduced forms show a complex pH dependence due to the presence of three ionizable residues (Glu-44, His-20, and His-42). Assignments have been made to specific residues and the spectral features compared to those of other bacterial HiPIP's. The decrease in the reduction potential with increasing pH for this class of proteins is attributed to stabilization of the oxidized state of the cluster by delocalization of electron density onto the neighboring Tyr-19 residue.
Arthur Amos Noyes Laboratory, California Institute of Technology, Pasadena 91125.
M
M
Sola
J A
JA
Cowan
H B
HB
Gray
D001426:Bacterial Proteins / Q000302:isolation & purification*; D002844:Chromatium / Q000032:analysis*; D004735:Energy Transfer; D005288:Ferredoxins / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D008667:Metalloproteins / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins; D012428:Ruthenium / Q000032:analysis*
D001426:Bacterial Proteins; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein; D012428:Ruthenium