Binding of molybdate to uteroferrin. Hyperfine interactions of the binuclear center with /sup 95/Mo, /sup 1/H, and /sup 2/H

Journal Article · Mon Apr 25 04:00:00 EDT 1988 · J. Biol. Chem.; (United States)

OSTI ID:7024757

Doi, K; McCracken, J; Peisach, J; Aisen, P

Uteroferrin, an acid phosphatase with a spin-coupled and redox-active binuclear iron center, is paramagnetic in its pink, enzymatically active, mixed-valence (S = 1/2) state. Phosphate, a product and inhibitor of the enzymatic activity of uteroferrin, converts the pink, EPR-active form of the protein to a purple, EPR-silent species. In contrast, molybdate, a tetrahedral oxyanion analog of phosphate, transforms the EPR spectrum of uteroferrin from a rhombic to an axial form. With both electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) spectroscopies, we observe a hyperfine interaction of (95Mo)molybdate with the S = 1/2, Fe(II)-Fe(III) center of the protein. A pair of 95Mo resonances centered at the 95Mo Larmor frequency at the applied magnetic field and separated by a hyperfine coupling constant of 1.2 MHz is evident. Therefore, a single monomeric species of molybdate is close to, and likely a ligand of, the binuclear cluster. 1H ENDOR studies on uteroferrin reveal at least six sets of lines mirrored about the 1H Larmor frequency. Two pairs of these lines become reduced in intensity when the protein is exchanged against D2O. Moreover, ESEEM and 2H ENDOR spectra display resonances at the 2H Larmor frequency. Therefore, the metal-binding region of the protein is accessible to solvent. Additional deuterium lines observable by ESEEM spectroscopy provide evidence for a population of strongly coupled, readily exchangeable protons associated with the binuclear center. The measured hyperfine coupling constants for these deuterons are orientation-dependent with splittings of nearly 4 MHz at g3 = 1.59 and less than 1 MHz at g1 = 1.94. In the presence of molybdate, ESEEM spectra of D2O-exchanged samples reveal a resonance at the 2H Larmor frequency, with no evidence of spectral components due to strongly coupled deuterons.

• Research Organization: Albert Einstein College of Medicine, Bronx, NY (USA)
• OSTI ID: 7024757
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:12; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACID PHOSPHATASE
ANIMALS
BIOCHEMICAL REACTION KINETICS
DEUTERIUM
DOMESTIC ANIMALS
ELECTRON SPIN RESONANCE
ELEMENTS
ENZYMES
ESTERASES
EVEN-ODD NUCLEI
HEAVY WATER
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNETIC RESONANCE
MAMMALS
METALLOPROTEINS
METALS
MOLYBDENUM
MOLYBDENUM 95
MOLYBDENUM ISOTOPES
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATASES
PROTEINS
REACTION KINETICS
RESONANCE
SPECTROPHOTOMETRY
STABLE ISOTOPES
SWINE
TRACER TECHNIQUES
TRANSITION ELEMENTS
VERTEBRATES
WATER