The GAP-related domain of the neurofibromatosis type 1 gene product interacts with ras p21.
The neurofibromatosis type 1 (NF1) protein contains a region of significant sequence similarity to ras p21 GTPase-activating protein (GAP) and the yeast IRA1 gene product. A fragment of NF1 cDNA encoding the GAP-related domain (NF1 GRD) was expressed, immunoaffinity purified, and assayed for effects on N-ras p21 GTPase activity. The GTPase of wild-type ras p21 was stimulated by NF1 GRD, but oncogenic mutants of ras p21 (Asp-12 and Val-12) were unaffected, and the GTPase of an effector mutant (Ala-38) was only weakly stimulated. NF1 GRD also down-regulated RAS function in S. cerevisiae. The affinity of NF1 GRD for ras p21 was estimated to be 250 nM: this is more than 20-fold higher than the affinity of GAP for ras p21. However, its specific activity was about 30 times lower. These kinetic measurements suggest that NF1 may be a significant regulator of ras p21 activity, particularly at low ras p21 concentrations.
Martin
G A
GA
Department of Molecular Biology, Cetus Corporation, Emeryville, California 94608.
Viskochil
D
D
Bollag
G
G
McCabe
P C
PC
Crosier
W J
WJ
Haubruck
H
H
Conroy
L
L
Clark
R
R
O'Connell
P
P
Cawthon
R M
RM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D003001:Cloning, Molecular; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009456:Neurofibromatosis 1 / Q000235:genetics*; D025542:Neurofibromin 1; D015345:Oligonucleotide Probes; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014162:Transfection; D020703:ras GTPase-Activating Proteins
D020690:GTPase-Activating Proteins; D025542:Neurofibromin 1; D015345:Oligonucleotide Probes; D011506:Proteins; D020703:ras GTPase-Activating Proteins; D006165:Guanylyl Imidodiphosphate; D020558:GTP Phosphohydrolases; D015689:Oncogene Protein p21(ras)