Linked Life Data

6286670

Source:http://linkedlifedata.com/resource/pubmed/id/6286670

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
18
pubmed:dateCreated
1982-10-29
pubmed:abstractText
The ATP analog 6-[(3-carboxy-4-nitrophenyl)thiol]-9-beta-D-ribofuranosylpurine 5'-triphosphate (Nbs6ITP) is slowly hydrolyzed at pH 7.4 by the (Na+ + K+)-ATPase, whereas it binds covalently at pH 8.5 and inhibits the enzyme irreversibly. Time courses of irreversible inhibition could only be fitted to a model in which the enzyme can exist in two slowly interchangeable states, one of which is enzymatically active and binds Nbs6ITP first reversibly and then covalently. Arguments that the covalent binding occurs at a low affinity nucleotide binding site are: (a) similarity of the Ki Nbs6ITP for the reversible and the irreversible inhibition and of K0.5 for ATP protection; (b) stoichiometry of covalent Nbs6ITP binding per alpha subunit of 0.8; and (c) change of complex substrate dependence of the enzyme to a Michaelis-Menten type after Nbs6ITP modification. This change in kinetics and the finding that the Nbs6ITP inactivation at a low affinity nucleotide binding site is increased by micromolar ADP concentrations indicates that the (Na+ + K+)-ATPase contains two different nucleotide binding sites. Since studies of nucleotide effects on enzyme inactivation by 5,5'-dithiobis(2-nitrobenzoic acid) did not confirm the hypothesis of an SH-group in a nucleotide binding site, Nbs6ITP may bind to another functional group, e.g. to an OH-group of tyrosine.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
257
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
10733-41
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1982
pubmed:articleTitle
Different classes of nucleotide binding sites in the (Na+ + K+)-ATPase studied by affinity labeling and nucleotide-dependent SH-group modifications.
pubmed:publicationType
Journal Article