N-Ras lipopeptides

For instance, in a synthesis of N-Ras lipopeptide 8, the choline ester in the palmitoylated tripeptide 5 was removed selectively and in high yield by means of the butyryl choline esterase (BChE). Efficient cou-... 

In a related experiment CV-1 fibroblasts were incubated with fluorescent N-Ras lipopeptides bearing a free palmitoylation site. These peptides cause staining of the CV-1 plasma membrane and efficient S-acylation even if the farnesyl group was replaced by a n-octyl group.1271 The association of the N-Ras lipopeptides with the plasma membrane... 

Chemoenzymatic Synthesis of Fluorescent N-Ras Lipopeptides and Their Use in Membrane Localization Studies In Vivo, H. Waldmann, M. Schelhaas, E. Nagele, J. Kuhlmann, A. Wittinghofer, H. Schroeder, J. R. Silvius, Angew. Chem. 1997,109, 2334-2337, Angew. Chem. Int. Ed. 1997,36,2238-2241. 

Nagele E, Schelhaas M, Kuder N, Waldmann H. Chemoen-zymatic synthesis of N-Ras lipopeptides. J. Am. Chem. Soc. 1998 120 6889-6902. 

As well as fluorescence-based assays, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In a commercial BIA-core system [231] a hydrophobic SPR sensor with an alkane thiol surface was incubated with vesicles of defined size distribution generating a hybrid membrane by fusion of the lipid vesicles with the alkane thiol layer [232]. If the vesicles contain biotinylated lipopeptides their membrane anchoring can be analyzed by incubation with streptavidine. Accordingly, experiments with lipopeptides representing the C-terminal sequence of N-Ras show clear differences between single and double hydrophobic modified peptides in their ability to persist in the lipid layer [233]. 

The insertion stability of several lipopeptides of the C-terminal sequence of N-Ras in such an artificial membrane is shown in Scheme 14. Here strepta-vidine is applied to indicate biotinylated lipopetides on the membrane surface. 

Eukaryotic cells utilize an efficient transport system that delivers macromolecules fast and secure to their destination. In the case of the small GTP binding proteins of the Ras family the modified C-terminus seems to be sufficient for addressing the polypeptide to its target membrane (in the case of Ras itself the plasma membrane). Lipopeptides with the C-terminal structure of N-Ras (either a pen-tamer with a C-terminal carboxymethylation and farnesylation or a heptapeptide with a palmitoyl thioester in addition) and a N-terminal 7-nitrobenz-2-oxa-l,3-diazolyl (NBD) fluorophore were microin-jected into NIH3T3 fibroblast cells and the distribution of the fluorophore was monitored by confocal laser fluorescence microscopy. Enrichment of the protein in the plasma membrane was efficient only for peptides with two hydrophobic modification sites, while the farnesylated but not palmitoylated peptide was distributed in the cytosol.1121... 

Synthesis of the Palmitoylated and Prenylated C-terminal Lipopeptides of the Human R- and N-Ras Proteins, T. Schmittberger, H. Waldmann, Bioorg. Med. Chem 1999, 7,749-762. 

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