N-ras protein

Synthesis of the Palmitoylated and Farnesylated C-Terminal Lipohexapeptide of the Human N-Ras Protein by Employing an Enzymatically Removable Urethane Protecting Group, H. Waldmann, E. Nagele, Angew. Chem. 1995,107, 2425-2428, Angew. Chem. Int. Ed. 1995, 34, 2259-2262. 

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. 

In addition to Ras, a number of other proteins are known to be substrates for FTase (many of unknown identity or function, determined by 2-D gel shift experiments in the presence and absence of FTI) these may also play a part in determining relative susceptibility to FTase inhibition.46 In particular, RhoB, a farnesylated protein involved with the formation of actin stress fibers and cytoskeletal organization, has been implicated in the growth-inhibitory consequences of FTase inhibition.47,48 Another study using the FTI 19 found that growth inhibition in soft agar of a panel of human tumor cell lines correlated with the mutational status of the H-and N-Ras proteins, but not with K-Ras mutations.49 In this study also, cells with genetic defects in addition to ras were sensitive to FTase inhibition. 

Reuther G, Tan K-T, Kohler J, Nowak C, Pampel A, Arnold K, Kuhlmann J, Waldmann H, Huster D. Backbone structure of the membrane binding lipid modified C-terminus of the human N-Ras protein. Angew. Chem. Int. Ed. 2006. Submitted. 

An application of the concept of combining enzyme-labile protecting groups with chemically labile ones is illustrated by the chemoenzymatic synthesis of the S-palmitoylated and S-farnesylated C-terminal lipohexapeptide of the human N-Ras protein (Scheme... 

Important issues of Ras functions remain to be clarified. The spectrum of known Ras-activated genes is certainly still very incomplete, and the tissue-specificity and cell-specificity of Ras proteins are ill defined. Furthermore, distinct members of the Ras subfamily appear to perform distinct functions that may overlap with other Ras proteins. Even within the genuine Ras proteins, the H-Ras, K-Ras and N-ras proteins, it has not yet been possible to discover functional differences. 

Scheme 5 Synthesis of N-Ras protein C-terminus for MIC ligation using hydiazide linker and Elhnan sulphonamide linker, (a) Cleavage of the hydrazide linker by oxidation and nucleophilic attack and Elhnan sulphonamide linker by activation and nucleophilic attack of a nucleophile, (b) Synthesis of famesylated and pahnitoylated N-Ras C-terminus with maleimido group using hydrazide linker and Ellman sulphonamide linker...

However, classical cleavage with a solution of methanol and DMAP leads to significant racemerization of cysteine. An alternative approach was to release the peptide from the solid support using H-Cys(Far)-OMe as a nucleophile with microwave irradiation for 10 min. Peptide corresponding to N-Ras protein C-terminus 13 was synthesized using Ellman sulfonamide linker strategy as shown in Scheme 5b (dotted line) [59, 60]. 

N-Ras proteins 63 with different modifications using the MIC ligation approach [78, 86, 91-93]. 

Fig. 1 (a) Semisynthetic N-Ras proteins with various C-tominal structures, (b) Cellular distribution and FRAP measurements of Cy5-N-Ras-PalFar and Cy5-N-Ras-HDFar at the Golgi. GalT is a Golgi marker... 

A. Vogel, G. Reuther, M.B. Roark, K.T. Tan, H. Waldmann, S.E. Feller, D. Huster, Backbone conformational flexibility of the lipid modified membrane anchor of the human N-Ras protein investigated by solid-state NMR and molecular dynamics sim-rflation, Biochim. Biophys. Acta 1798 (2010) 275—285. 

Figure 2 Chemoenzymatic synthesis of S-pahnitoylated and 5-famesylated C-terminal lipohexa-peptide of the human N-Ras protein.

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