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J Am Chem Soc. 2017 Jun 7;139(22):7632-7639. doi: 10.1021/jacs.7b02988. Epub 2017 May 22.

Total Chemical Synthesis and Folding of All-l and All-d Variants of Oncogenic KRas(G12V).

Author information

1
Tri-Institutional PhD Program in Chemical Biology, Weill Cornell Medical College , New York, New York 10065, United States.
2
Departments of Molecular and Cellular Biology, Stem Cell and Regenerative Biology, and Chemistry and Chemical Biology, Harvard University and Harvard Medical School , Cambridge, Massachusetts 02138, United States.
3
Department of Chemistry, Columbia University , Havemeyer Hall, 3000 Broadway, New York, New York 10027, United States.

Abstract

The Ras proteins are essential GTPases involved in the regulation of cell proliferation and survival. Mutated oncogenic forms of Ras alter effector binding and innate GTPase activity, leading to deregulation of downstream signal transduction. Mutated forms of Ras are involved in approximately 30% of human cancers. Despite decades of effort to develop direct Ras inhibitors, Ras has long been considered "undruggable" due to its high affinity for GTP and its lack of hydrophobic binding pockets. Herein, we report a total chemical synthesis of all-l- and all-d-amino acid biotinylated variants of oncogenic mutant KRas(G12V). The protein is synthesized using Fmoc-based solid-phase peptide synthesis and assembled using combined native chemical ligation and isonitrile-mediated activation strategies. We demonstrate that both KRas(G12V) enantiomers can successfully fold and bind nucleotide substrates and binding partners with observable enantiodiscrimination. By demonstrating the functional competency of a mirror-image form of KRas bound to its corresponding enantiomeric nucleotide triphosphate, this study sets the stage for further biochemical studies with this material. In particular, this protein will enable mirror-image yeast surface display experiments to identify all-d peptide ligands for oncogenic KRas, providing a useful tool in the search for new therapeutics against this challenging disease target.

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