Linked Life Data

1847680

Source:http://linkedlifedata.com/resource/pubmed/id/1847680

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1991-4-2
pubmed:abstractText
Tetrammine cobalt(III) phosphate [Co(NH3)4PO4] inactivates Na+/K(+)-ATPase in the E2 conformational state, dependent on time and concentration, according to Eqn (1): Co(NH3)4PO4 + E2 Kd in equilibrium E2.Co(NH3)4PO4k2----E'2.Co(NH3)4PO4. The inactivation rate constant k2 for the formation of a stable E'2.Co(NH3)4PO4 at 37 degrees C was 0.057 min-1; the dissociation constant, Kd = 300 microM. The activation energy for the inactivation process was 149 kJ/mol. ATP and the uncleavable adenosine 5'-[beta, gamma-methylene]triphosphate competed with Co(NH3)4PO4 for its binding site with Ks = 0.41 mM and 5 mM, respectively. MgPO4 competed with Co(NH3)4PO4 linearly, with Ks = 50 microM, as did phosphate (Ks = 16 mM) and Mg2+ (Ks = 160 microM). It is concluded that the MgPO4 analogue binds to the MgPO4-binding subsite of the low-affinity ATP-binding site (of the E2 conformation). Also, Na+ (Ks = 860 microM) protected the enzyme against inactivation in a competitive manner. From the intersecting (slope and intercept linear) noncompetitive effect of Na+ against the inactivation by Co(NH3)4PO4, apparent affinities of K+ for the free enzyme of 41 microM, and for the E.Co(NH3)4PO4 complex of 720 microM, were calculated. Binding of Co(NH3)4PO4 to the enzyme inactivated Na+/K(+)-ATPase and K(+)-activated phosphatase, and, moreover, prevented the occlusion of 86Rb+; however, the activity of the Na(+)-ATPase, the phosphorylation capacity of the high-affinity ATP-binding site and the ATP/ADP-exchange reaction remained unchanged. With Co(NH3)432PO4 a binding capacity of 135 pmol unit enzyme was found. Phosphorylation and complete inactivation of the enzyme with Co(NH3)432PO4 or the 32P-labelled tetramminecobalt ATP ([gamma-32P]Co(NH3)4ATP) at the low-affinity ATP-binding site, allowed (independent of the purity of the Na+/K(+)-ATPase preparation) a further incorporation of radioactivity from 32P-labelled tetraaquachromium(III) ATP ([gamma-32P]CrATP) to the high-affinity ATP-binding site with unchanged phosphorylation capacity. However, inactivation and phosphorylation of Na+/K(+)-ATPase by [gamma-32P]CrATP prevented the binding of Co(NH3)4 32PO4 or [gamma-32P]Co(NH3)4ATP to the enzyme. [gamma-32P]CO(NH3)4ATP and Co(NH3)432PO4 are mutually exclusive. The data are consistent with the assumption of a cooperation of catalytic subunits within an (alpha,beta)2-diprotomer, which change their interactions during the Na+/K(+)-pumping process. Our findings seem not to support a symmetrical Repke and Stein model of enzyme action.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
195
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
407-19
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed-meshheading:1847680-Adenosine Triphosphate, pubmed-meshheading:1847680-Animals, pubmed-meshheading:1847680-Binding, Competitive, pubmed-meshheading:1847680-Binding Sites, pubmed-meshheading:1847680-Cobalt, pubmed-meshheading:1847680-Enzyme Activation, pubmed-meshheading:1847680-Enzyme Stability, pubmed-meshheading:1847680-Kidney Medulla, pubmed-meshheading:1847680-Kinetics, pubmed-meshheading:1847680-Magnesium, pubmed-meshheading:1847680-Magnesium Compounds, pubmed-meshheading:1847680-Models, Biological, pubmed-meshheading:1847680-Phosphates, pubmed-meshheading:1847680-Potassium Chloride, pubmed-meshheading:1847680-Protein Conformation, pubmed-meshheading:1847680-Quaternary Ammonium Compounds, pubmed-meshheading:1847680-Sodium Chloride, pubmed-meshheading:1847680-Sodium-Potassium-Exchanging ATPase, pubmed-meshheading:1847680-Swine
pubmed:year
1991
pubmed:articleTitle
Phosphate binding and ATP-binding sites coexist in Na+/K(+)-transporting ATPase, as demonstrated by the inactivating MgPO4 complex analogue Co(NH3)4PO4.
pubmed:affiliation
Institut für Biochemie und Endokrinologie, Justus-Liebig-Universität Giessen, Federal Republic of Germany.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't