Electron paramagnetic resonance studies of the coordination schemes and site selectivities for divalent metal ions in complexes with pyruvate kinase

Journal Article · Tue Feb 20 04:00:00 EST 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00459a019· OSTI ID:6897382

Buchbinder, J L; Reed, G H ^[1]

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1. Univ. of Wisconsin, Madison (USA)

Electron paramagnetic resonance (EPR) spectroscopy has been used to investigate the properties of the binuclear divalent metal center at the active site of pyruvate kinase. The preferred binding sites for different types of divalent cation in complexes of the enzyme with ATP and oxalate were determined in hybrid metal complexes with Mn(II). Superhyperfine coupling between the unpaired electron spin of Mn(II) and the nuclear spin of {sup 17}O in isotopically enriched forms of oxalate and ATP was used to determine the position of Mn(II) at the binuclear metal center. When Mn(II) is present in combination with Zn(II), Ni(II), or Co(II), Mn(II) binds predominantly at the site defined by ligands from the protein, oxalate, and the {gamma}-phosphate of ATP. In contrast, EPR data of samples with mixtures of Mn(II)/Ca(II) or Mn(II)/Cd(II) reveal signals of two distinct hybrid-metal complexes. The results indicate that, in enzymic complexes with ATP and oxalate, the relative size of the cation is a major factor controlling site selectivity. Metal ions that have ionic radii smaller than Mn(II) bind preferentially at the site occupied by ATP whereas metal ions that have ionic radii larger than Mn(II) bind preferentially at the site occupied by oxalate. EPR data of one of the hybrid complexes formed by Cd(II) and Mn(II) show that an {alpha},{beta},{gamma}-tridentate species of Mn{sup II} ATP binds to the enzyme. The finding that Mn(II) at either of the divalent cation sites binds to the {gamma}-phosphate group of ATP suggests that the {gamma}-phosphate is linked to both divalent cations in the binuclear divalent metal center.

• OSTI ID: 6897382
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:7; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPLEXES
ATP
CADMIUM COMPLEXES
CALCIUM COMPLEXES
CARBOXYLIC ACIDS
CATIONS
CHARGED PARTICLES
COMPLEXES
ELECTRON SPECTRA
ELECTRON SPIN RESONANCE
ENZYMES
EVEN-ODD NUCLEI
IONS
ISOTOPES
KETO ACIDS
LIGHT NUCLEI
MAGNESIUM COMPLEXES
MAGNETIC RESONANCE
MAGNETISM
MANGANESE COMPLEXES
NICKEL COMPLEXES
NUCLEI
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN 17
OXYGEN ISOTOPES
PARAMAGNETISM
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
PYRUVIC ACID
RESONANCE
SPECTRA
STABLE ISOTOPES
TRANSFERASES
TRANSITION ELEMENT COMPLEXES
ZINC COMPLEXES