Regulation of the GTPase activity of the ras-related rap2 protein.
The small GTP-binding protein rap2A exhibits a high level of identity with rap1 and ras proteins (60% and 46%, respectively). Nevertheless, its intrinsic GTPase activity is not stimulated by ras-GAP, and unlike the rap1A protein, it cannot compete with ras proteins for their interaction with ras-GAP. In addition, rap1-GAPm that is highly active on the GTPase activity of the rap1A product, also stimulates the GTPase activity of the rap2A protein but with a 30-40-fold lower efficiency. An activity that greatly stimulated the GTPase activity of the rap2 protein (rap2-GAP) was found in bovine brain cytosol and purified. However, it copurified with the cytosolic form of rap1-GAP and was more efficient at stimulating the GTPase activity of the rap1 protein; this 55 kD polypeptide, that is recognized by an antibody raised against rap1-GAPm, likely represents a degraded and soluble form of the full size 89 kD molecule. In bovine brain membranes, a weak GAP activity toward the rap2A protein was also detected; however, it was also attributable to the membrane-associated rap1-GAPm. Thus, it appears that a single rap-GAP protein, complete or degraded, is able to stimulate the GTPase activity of both rap1 and rap2 proteins.
Janoueix-Lerosey
I
I
INSERM U-248, Faculté de Médecine Lariboisière-Saint-Louis, Paris, France.
Polakis
P
P
Tavitian
A
A
de Gunzburg
J
J
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007313:Insecta; D007700:Kinetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection; D020668:rap GTP-Binding Proteins
D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D020668:rap GTP-Binding Proteins