Abstract
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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have