A novel 110-kDa maternal CAAX box-containing protein from Xenopus is palmitoylated and isoprenylated when expressed in baculovirus.
We describe a unique 110-kDa protein, xlcaax-1, that is a member of a group of membrane-associated proteins such as the ras and ras-related proteins and nuclear lamins. Many of these proteins are involved in signal transduction or cell signaling, possess a C-terminal CAAX box, and undergo fatty acid acylation (Glomset, J. A., Gelb, M. H., and Farnsworth, C. C. (1990) Trends Biochem. Sci. 15, 139-142). The ras and ras-related proteins bind GTP and in most cases are both isoprenylated and palmitoylated. The xlcaax-1 protein possesses a C-terminal CAAX sequence that is identical to the N-ras protein. In addition to the CAAX box, xlcaax-1 contains a series of basic amino acids upstream of the CAAX sequence similar to several nonpalmitoylated forms of the ras-related proteins. When the xlcaax-1 cDNA is expressed in a baculovirus expression system, the product undergoes isoprenylation and palmitoylation utilizing a mechanism similar to that of the ras proteins. In addition, the xlcaax-1 protein is isoprenylated, and a minor fraction is palmitoylated in Xenopus XTC tissue culture cells. We have also demonstrated that the protein is associated with membrane fractions in full-grown Xenopus oocytes and in Xenopus XTC tissue culture cells and that membrane association is isoprenylation-dependent. The presence of maternal molecules possessing signal transduction potential is an attractive mechanism for modulating the effects of growth factors and other signal molecules during development.
Kloc
M
M
Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, Houston.
Reddy
B
B
Crawford
S
S
Etkin
L D
LD
D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D002460:Cell Line; D002855:Chromatography, Thin Layer; D003001:Cloning, Molecular; D007545:Isoproterenol / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010169:Palmitic Acids / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D014981:Xenopus; D029867:Xenopus Proteins
D008565:Membrane Proteins; C068700:PALM3 protein, Xenopus; D010169:Palmitic Acids; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D007545:Isoproterenol