The C-terminal polylysine region and methylation of K-Ras are critical for the interaction between K-Ras and microtubules.


Journal Article

After synthesis in the cytosol, Ras proteins must be targeted to the inner leaflet of the plasma membrane for biological activity. This targeting requires a series of C-terminal posttranslational modifications initiated by the addition of an isoprenoid lipid in a process termed prenylation. A search for factors involved in the intracellular trafficking of Ras has identified a specific and prenylation-dependent interaction between tubulin/microtubules and K-Ras. In this study, we examined the structural requirements for this interaction between K-Ras and microtubules. By using a series of chimeras in which regions of the C terminus of K-Ras were replaced with those of Ha-Ras and vice versa, we found that the polylysine region of K-Ras located immediately upstream of the prenylation site is required for binding of K-Ras to microtubules. Studies in intact cells confirmed the importance of the K-Ras polylysine region for microtubule binding, as deletion or replacement of this region resulted in loss of paclitaxel-induced mislocalization of a fluorescent K-Ras fusion protein. The additional modifications in the prenyl protein processing pathway also affected the interaction of K-Ras with microtubules. Removal of the three C-terminal amino acids of farnesylated K-Ras with the specific endoprotease Rce1p abolished its binding to microtubules. Interestingly, however, methylation of the C-terminal prenylcysteine restored binding. Consistent with these results, localization of the fluorescent K-Ras fusion protein remained paclitaxel-sensitive in cells lacking Rce1, whereas no paclitaxel effect was observed in cells lacking the methyltransferase. These studies show that the polylysine region of K-Ras is critical for its interaction with microtubules and provide the first evidence for a functional consequence of Ras C-terminal proteolysis and methylation.

Full Text

Duke Authors

Cited Authors

  • Chen, Z; Otto, JC; Bergo, MO; Young, SG; Casey, PJ

Published Date

  • December 29, 2000

Published In

Volume / Issue

  • 275 / 52

Start / End Page

  • 41251 - 41257

PubMed ID

  • 11007785

Pubmed Central ID

  • 11007785

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M006687200


  • eng

Conference Location

  • United States