Abstract
Resonance Raman and electron paramagnetic resonance spectroscopy have been utilized to identify histidine as an axial heme ligand in a high spin, heme c-containing protein isolated from the photosynthetic purple sulfur bacterium Chromatium vinosum. Resonance Raman spectroscopy has also been used to characterize the CO adduct of the C. vinosum hemoprotein. Resonance Raman spectra of the heme site obtained within 10 ns of CO photolysis from the ferrous hemoprotein are virtually identical to those of the unligated protein, indicating that there is little or no rearrangement of the heme pocket in response to ligand photolysis. The equilibrium constant for CO binding to the ferrous hemeprotein was measured to be 1.7 X 10(-5) M-1 and the CO association rate constant determined to be 5.4 X 10(3) M-1 S-1. The quantum efficiency for photodissociation of the hemoprotein X CO complex was greater than or equal to 0.9.
Highlights
Resonance Raman and electron paramagnetic resonance spectroscopy have been utilizedto identify histidine as an axial heme ligandin a high spin, hemeccontaining protein isolated from the photosynthetic purple sulfur bacterium Chromatiurn vinosum
The equilibrium constant for CO binding to the ferroushemeprotein was measured to be 1.7 X lom5 and Giacometti [3], using the apparatus described by Olson et al [4] and myoglobin as a standard with quantum yield equal to 1.0.All rapid mixing experiments were carried out with a Gibson-Durrum stopped flow spectrophotometer that was interfaced via a 12 bit AjD converter to anOLIS Model 3820data collection system
Comparison of association rate constants and equilibrium constants for carbon monoxide binding to a uariety of hemoproteins
Summary
Vol 262, No 3, Issue of January 25, pp. 1144-1147,1987 Printed in U.S.A. Spectroscopic and Kinetic Propertieosf an Oxygen-binding Heme Protein from Chromatiurn vinosum”. OndriasQll, EriWc. FindsenQG, raham PalmerlJJ, ohn S. KnaffSll. From the #Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, the $Department of Chemistry, University of New Mexico,Albwuewue. New Mexico 87131, and the llDepartment of Biochemistry, Rice University,. Resonance Raman and electron paramagnetic resonance spectroscopy have been utilizedto identify histidine as an axial heme ligandin a high spin, hemeccontaining protein isolated from the photosynthetic purple sulfur bacterium Chromatiurn vinosum.
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