Characterization of a guanine nucleotide dissociation stimulator for a ras-related GTPase.
ras-related GTPases participate in signaling for a variety of cellular processes. The GTPases cycle between a GTP-bound active state and a GDP-bound inactive state. This cycling is partially controlled by guanine nucleotide dissociation stimulators (GDS, also known as exchange factors). We report on the molecular cloning of cDNAs encoding a new mammalian GDS protein, using sequences derived from the yeast ras GDS proteins as probes. The encoded protein stimulates the dissociation of guanine nucleotides from the ras-related ralA and ralB GTPases at a rate at least 30-fold faster than the intrinsic nucleotide dissociation rate. This new GDS, ralGDS, is at least 20-fold more active on the ralA and ralB GTPases than on any other GTPase tested, including other members of the ras family (H-ras, N-ras, K-ras, R-ras, rap1a and rap2), members of the rho family (rhoA, rhoB and CDC42-Hs) and members of the rab family (rab3a and ypt1). While the ralGDS protein is phosphorylated on serine residues, we find no evidence that phosphorylation affects the activity of insect cell-expressed ralGDS towards the ralA or ralB GTPase. The 3600 nucleotide ralGDS mRNA and the 115 kDa protein were found in all tissues and cell lines examined.
Albright
C F
CF
Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142.
Giddings
B W
BW
Liu
J
J
Vito
M
M
Weinberg
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005822:Genetic Vectors; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007313:Insecta; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009838:Oligodeoxyribonucleotides; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D014162:Transfection; D020726:ral Guanine Nucleotide Exchange Factor; D020668:rap GTP-Binding Proteins
D005656:Fungal Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D020726:ral Guanine Nucleotide Exchange Factor; D006153:Guanosine Diphosphate; D011061:Poly A; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins