Two-dimensional magnetization exchange spectroscopy of Anabaena 7120 ferredoxin. Nuclear Overhauser effect and electron self-exchange cross peaks from amino acid residues surrounding the Fe-2S* cluster
- National Magnetic Resonance Facility, Madison, WI (United States) Univ. of Wisconsin, Madison (United States)
Hyperfine {sup 1}H NMR signals of the 2 Fe-2S* vegetative ferredoxin from Anabaena 7,120 have been studied by two-dimensional (2D) magnetization exchange spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu{sup 27}, Arg{sup 42}, and Ala{sup 43} on the basis of the X-ray coordinates of oxidized Anabaena 7,120 ferredoxin. Three chemical exchange cross peaks were detected in magnetization exchange spectra of half-reduced ferredoxin and assigned to the {sup 1}H{sup {alpha}} protons of Cys{sup 49} and Cys{sup 79} (both of whose sulfur atoms are ligated to Fe(III)) and Arg{sup 42} (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical exchange cross peaks provide a means of extending assignments in the spectrum of reduced ferredoxin to assignments in the spectrum of the oxidized protein. The results suggest that 2D magnetization exchange spectroscopy employing short mixing times will be useful for the assignment and characterization of hyperfine {sup 1}H peaks in a variety of paramagnetic proteins.
- OSTI ID:
- 5013742
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:30; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
ALANINES
ALGAE
AMINO ACIDS
ARGININE
BARYONS
CARBOXYLIC ACIDS
CHEMICAL SHIFT
COMPLEXES
ELEMENTARY PARTICLES
FERMIONS
FERREDOXIN
HADRONS
HEAVY WATER
HYDROGEN COMPOUNDS
HYPERFINE STRUCTURE
IRON COMPLEXES
LEUCINE
MAGNETIC RESONANCE
MAGNETIZATION
METALLOPROTEINS
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OVERHAUSER EFFECT
OXYGEN COMPOUNDS
PLANTS
PROTEINS
PROTONS
RELAXATION TIME
RESONANCE
SULFUR COMPLEXES
TRANSITION ELEMENT COMPLEXES
WATER