Purification and characterization from bovine brain cytosol of two GTPase-activating proteins specific for smg p21, a GTP-binding protein having the same effector domain as c-ras p21s.
The smg-21 GTP-binding protein (smg p21) has the same effector domain as the ras proteins (ras p21s) and is identical with the proteins of the rap1A and Krev-1 genes. In this paper, two proteins stimulating the GTPase activity of smg p21 are partially purified from bovine brain cytosol. These proteins, designated as smg p21 GTPase-activating protein (GAP) 1 and 2, are separated from a c-ras p21 GAP described previously by column chromatographies. smg p21 GAP1 and -2 stimulate the GTPase activity of only smg p21 but not that of c-Ha-ras p21 or the rho and smg-25A GTP-binding proteins. smg p21 GAP1 or -2 does not stimulate the dissociation of guanosine 5'-3-O-(thio)triphosphate or GDP from smg p21. smg p21 GAP1 or -2 themselves do not have GTP/GDP binding or GTPase activity. The Mr values of smg p21 GAP1 and -2 are estimated to be 250-400 x 10(3) and 80-100 x 10(3) by gel filtration and sucrose density gradient ultracentrifugation, respectively. The activity of smg p21 GAP1 and -2 is killed by tryptic digestion or heat boiling. These results indicate that bovine brain contains two smg p21 GAPs in addition to c-ras p21 GAP.
Kikuchi
A
A
Department of Biochemistry, Kobe University School of Medicine, Japan.
Sasaki
T
T
Araki
S
S
Hata
Y
Y
Takai
Y
Y
D000818:Animals; D001792:Blood Platelets / Q000032:analysis; D001923:Brain Chemistry; D002417:Cattle; D003600:Cytosol / Q000032:analysis*; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras)
D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases; D016283:Proto-Oncogene Proteins p21(ras)