Characterization of GTP binding and hydrolysis in plasma membranes of zucchini.
We have investigated the possibility that G-protein-like entities may be present in the plasma membrane (PM) of zucchini (Cucurbita pepo L.) hypocotyls by examining a number of criteria common to animal and yeast G-proteins.  The GTP binding and hydrolysis characteristics of purified zucchini PM are similar to the characteristics of a number of known G-proteins.  Our results demonstrate GTP binding to a single PM site having a Kd value between 16-31 nM.  This binding has a high specificity for guanine nucleotides, and is stimulated by Mg2+, detergents, and fluoride or aluminium ions.  The GTPase activity (Km = 0.49 micromole) of zucchini PM shows a sensitivity to NaF similar to that seen for other G-proteins.  Localization of GTP mu 35S binding to nitrocellulose blots of proteins separated by SDS-PAGE indicates a 30-kDa protein as the predominant GTP-binding species in zucchini PM.  Taken together, these data indicate that plant PM contains proteins which are biochemically similar to previously characterized G-proteins.
Perdue
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DO
Department of Botany and Plant Pathology, Oregon State University, Corvallis, USA.
Lomax
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D000535:Aluminum / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D003902:Detergents / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D006150:Guanine Nucleotides / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D018546:Hypocotyl / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding; D015398:Signal Transduction / Q000502:physiology*; D014675:Vegetables / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D003902:Detergents; D006150:Guanine Nucleotides; D008565:Membrane Proteins; D006160:Guanosine Triphosphate; D000535:Aluminum; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D008274:Magnesium; D005459:Fluorides