Abstract
Purified guanine nucleotide-binding regulatory proteins, as either the oligomers or the isolated nucleotide-binding alpha subunits, display anomalous kinetics of nucleotide binding. This is due to the presence of tightly bound GDP in these preparations. The dissociation of bound GDP is the rate-limiting step for nucleotide binding. GDP can be removed by chromatography in the presence of 1 M (NH4)2SO4 and 20% glycerol, which yields preparations of G proteins that contain less than 0.1 mol of GDP/mol of guanosine 5'-(gamma-thio)triphosphate (GTP gamma S)-binding site. When the GDP is removed, the binding of GTP gamma S displays kinetics consistent with a bimolecular reaction.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Ammonium Sulfate / pharmacology
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GTP-Binding Proteins / analysis
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GTP-Binding Proteins / metabolism*
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Glycerol / pharmacology
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Guanine Nucleotides / analysis*
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Guanine Nucleotides / metabolism*
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Guanosine 5'-O-(3-Thiotriphosphate)
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Guanosine Diphosphate / analysis*
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Guanosine Diphosphate / isolation & purification
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Guanosine Triphosphate / analogs & derivatives
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Guanosine Triphosphate / metabolism
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Kinetics
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Thionucleotides / metabolism
Substances
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Guanine Nucleotides
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Thionucleotides
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Guanosine Diphosphate
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Guanosine 5'-O-(3-Thiotriphosphate)
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Guanosine Triphosphate
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GTP-Binding Proteins
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Glycerol
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Ammonium Sulfate