title: GTPase activating proteins for the smg-21 GTP-binding protein having the same effector domain as the ras proteins in human platelets.
abstract: Two proteins stimulating the GTPase activity of the smg-21 GTP-binding protein (smg p21) having the same effector domain as the ras proteins (ras p21s) are partially purified from the cytosol fraction of human platelets. These proteins, designated as smg p21 GTPase activating protein (GAP) 1 and 2, do not stimulate the GTPase activity of c-Ha-ras p21. The GAP activity for c-Ha-ras p21 is also detected in the cytosol fraction of human platelets. smg p21 GAP1 and 2 are separated from c-Ha-ras p21 GAP by column chromatographies. The activity of smg p21 GAP1 and 2 is killed by tryptic digestion or heat boiling. The Mr values of smg p21 GAP1 and 2 are similar and are estimated to be 2.5-3.5 x 10(5) by gel filtration analysis. These results indicate that there are two GAPs for smg p21 in addition to a GAP for c-Ha-ras p21 in human platelets.
authors.affiliation: Department of Biochemistry, Kobe University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ueda
authors.forename: A
authors.initials: A
authors.lastname: Kikuchi
authors.forename: N
authors.initials: N
authors.lastname: Ohga
authors.forename: J
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000097:blood* / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011506:Proteins / Q000302:isolation & purification; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D020668:rap GTP-Binding Proteins
chemical_list: D001798:Blood Proteins; D008565:Membrane Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D020668:rap GTP-Binding Proteins