Methylation and proteolysis are essential for efficient membrane binding of prenylated p21K-ras(B). |
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| Authors: | J F Hancock K Cadwallader C J Marshall |
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| Affiliation: | Department of Haematology, Royal Free Hospital School of Medicine, London, UK. |
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| Abstract: | Plasma membrane targeting of p21K-ras(B) requires a CAAX motif and a polybasic domain. The CAAX box directs a triplet of post-translational modifications: farnesylation, proteolysis of the AAX amino acids and methylesterification. These modifications are closely coupled in vivo. However, in vitro translation of mRNA in rabbit reticulocyte lysates produces p21K-ras(B) proteins which are arrested in processing after farnesylation. Intracellular membranes are then required both for proteolytic removal of the AAX amino acids and methylesterification of farnesylated p21K-ras(B). Binding of p21K-ras(B) to plasma membranes in vitro can then be shown to depend critically on AAX proteolysis and methylesterification since p21K-ras(B) which is farnesylated, but not methylated, binds inefficiently to membranes. |
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