Biomaterial Database

Effects of monovalent cations and divalent metal ions on Escherichia coli selenophosphate synthetase. 1994

I Y Kim, and T C Stadtman

Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.

A labile selenium donor compound, selenophosphate, is formed from selenide and ATP by selenophosphate synthetase. A divalent metal ion, Mg2+, and a monovalent cation, K+, NH4+, or Rb+, are required for selenophosphate synthetase activity [Veres, Z., Kim, I. Y., Scholz, T. D. & Stadtman, T. C. (1994) J. Biol. Chem. 269, 10597-10603]. Na+ and Li+ are ineffective as activators and in the presence of K+ are inhibitory. Mn-ATP, although not able to replace Mg-ATP for catalytic activity, binds to the enzyme provided an active monovalent cation is present. No Mn-ATP is bound when K+ is replaced with Na+. The requirement for K+, both for Mn-ATP binding and for catalytic activity of the synthetase, indicates a specific monovalent cation-induced conformational state of the enzyme. Previously we reported that activity of the enzyme is markedly inhibited by micromolar levels of Zn2+ in the presence of millimolar levels of Mg2+ [Kim, I. Y., Veres, Z. & Stadtman, T. C. (1993) J. Biol. Chem. 268, 27020-27025]. Binding of Mn-ATP also is decreased upon addition of Zn2+, indicating that the inhibitory effect of Zn2+ is exerted at the substrate-binding step of the overall selenophosphate synthetase reaction. When a cysteine residue at position 17 or 19 is replaced with serine, Mn-ATP binding to these mutant enzymes is unaffected by Zn2+ addition. Direct involvement of these cysteine residues in the zinc binding site was shown by use of 65ZnCl2. Radioactive Zn2+ bound to wild-type enzyme and was retained after gel filtration, but under the same conditions the catalytically inactive Cys-17 mutant protein and the catalytically active Cys-19 mutant enzyme were unlabeled.

UI	MeSH Term	Description	Entries
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008670	Metals	Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th ed)	Metal
D010770	Phosphotransferases	A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7.	Kinases,Phosphotransferase,Phosphotransferases, ATP,Transphosphorylase,Transphosphorylases,Kinase,ATP Phosphotransferases
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002414	Cations, Monovalent	Positively charged atoms, radicals or group of atoms with a valence of plus 1, which travel to the cathode or negative pole during electrolysis.	Monovalent Cation,Cation, Monovalent,Monovalent Cations
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D000644	Quaternary Ammonium Compounds	Derivatives of ammonium compounds, NH4+ Y-, in which all four of the hydrogens bonded to nitrogen have been replaced with hydrocarbyl groups. These are distinguished from IMINES which are RN	Quaternary Ammonium Compound,Ammonium Compound, Quaternary,Ammonium Compounds, Quaternary,Compound, Quaternary Ammonium
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial