Identification of localized redox states in plant-type two-iron ferrodoxins using the nuclear Overhauser effect
- Univ. of California, Davis (USA)
- Univ. of Florence (Italy)
The homonuclear Overhauser effect (NOE), in conjunction with nonselective spin-lattice relaxation measurements, has been employed to assign the contact-shifted resonances for the reduced form of two typical plant-type two-iron ferrodoxins from the algae Spirulina platensis and Porphyra umbilicalis. These results demonstrate that the NOE should have broad general applicability for the assignments and electronic structural elucidation of diverse subclasses of paramagnetic iron-sulfur cluster proteins. NOE connectivities were detected only among sets of resonances exhibiting characteristically different deviations from Curie behavior, providing strong support for the applicability of the spin Hamiltonian formulation for the NMR properties of the antiferromagnetically coupled iron clusters. The geminal {beta}-methylene protons for the two cysteines bound to the iron(II) center were clearly identified, as well as the C{sub {alpha}}H and one C{sub {beta}}H for each of the cysteines bound to the iron(III). The identification of the iron bound to cysteines 41 and 46 as the iron(II) in the reduced protein was effected on the basis of dipolar contacts between the bound cysteines. Resolved labile proton contact-shifted resonances are attributed to hydrogen bonding to the iron(III) center, and it is concluded that the contact-shifted resonances for the more numerous hydrogen bonds to the iron(II) center are not resolved from the diamagnetic envelope. The identification of the iron closer to the protein surface as the more reducible one is consistent with predictions based on a larger number of hydrogen bonds to this center.
- OSTI ID:
- 7100941
- Journal Information:
- Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:9; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALGAE
AMINO ACIDS
BARYONS
CARBOXYLIC ACIDS
CHEMICAL BONDS
CYSTEINE
ELEMENTARY PARTICLES
FERMIONS
FERREDOXIN
HADRONS
IRON COMPOUNDS
MAGNETIC RESONANCE
METALLOPROTEINS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OVERHAUSER EFFECT
PLANTS
PORPHYRA
PROTEINS
PROTONS
RELAXATION
RESONANCE
RHODOPHYCOTA
SPECTRA
SPIN-LATTICE RELAXATION
THIOLS
TRANSITION ELEMENT COMPOUNDS