Identification of the cDNA for xlcaax-1, a membrane associated Xenopus maternal protein.

xlcaax-1 is a cDNA coding for a CAAX box containing protein in Xenopus laevis that undergoes isoprenylation and palmitoylation. Here we report on the confirmation that this clone (formerly xlgv7) codes for a 110 kDa membrane associated protein and not an 80 kDa nuclear protein as originally believed (1). The reason for the misidentification was the presence of a common epitope on these two proteins recognized by the monoclonal antibody 37-1A9. We clarified the discrepancy by raising polyclonal antibodies against the xlcaax-1 protein produced in a bacterial expression system and demonstrating that these antibodies only recognize the 110 kDa protein on western blots of oocyte extracts. During early development xlcaax-1 protein starts reaccumulating from the neurula stage. In the adult frog both the xlcaax-1 protein and its cognate mRNA are highly enriched in the kidney. Consistent with the presence of CAAX box at the C-terminus this protein is associated with the membranes in Xenopus tissue culture cells (XTC).