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RAS Biochemistry and Biophysics

Model of RAS-RAF complex at the membrane

Credit: Que Van, NCI RAS Initiative

RAS proteins function through interactions with the inner plasma membrane, and with numerous interacting partner proteins. These interactions are not understood at atomic levels, and could hold the key to controlling RAS signaling in cancers. The goal of the Biochemistry and Biophysics group is to apply the most sensitive techniques to better understand how these interactions affect signaling by wild-type and mutant RAS.

Our Progress

Our group has characterized the interactions of fully modified KRAS4b protein with nanodiscs of different lipid compositions. Nanodiscs are a surrogate for cell membranes where the lipid composition can be completely specified. In addition, protein-nanodisc complexes are amenable to biophysical assays. Only fully modified KRAS protein can bind to nanodiscs.

Half a dozen different mutants of KRAS account for more than one million cancer deaths each year world-wide. Understanding the different mutant proteins in detail may help us understand why different KRAS mutants predominate in different cancers. Our group has measured the binding affinities and intrinsic hydrolysis rates of all the major oncogenic mutants of KRAS4b.

We have utilized opportunities to collaborate on research, including the characterization of KRAS proteins by NMR, analytical ultracentrifugation, neutron scattering, and single molecule analysis in artificial lipid bilayers. View the PubMed abstract on the characterization of fully modified KRAS4b protein.

Our Projects

  • Characterize the folding, activities, oligimerization states, and membrane interactions of purified wild-type and mutant RAS proteins
  • Characterize the interactions of RAS proteins with partner proteins such as RAF, NF1, RASA1, calmodulin, PDEdelta, and AGO2
  • Reconstitute the reactions mediated by RAS and RAS complexed with partner proteins

Tools We Use

  • Surface plasmon resonance
  • Mass spectrometry
  • Dynamic light scattering
  • RAS activity assays
  • Nanodiscs
  • NMR (with collaborators)
  • Neutron scattering (with collaborators)
  • Analytical ultracentrifugation (with collaborators)


The RAS Biochemistry and Biophysics Group has collaborated with:

Paul Henderson
University of California, Davis

Jay Groves
University of California, Berkeley

Steve Sligar
University of Illinois at Urbana-Champaign

Marco Tonelli
Nuclear Magnetic Resonance Facility at Madison, University of Wisconsin

Rodolfo Ghirlando
National Institute of Diabetes and Digestive Kidney Dieases (NIDDK)

Frank Heinrich
National Institute of Standards and Technology

Carla Mattos
Northeastern University

Michael Gross
Washington University, St. Louis

Chris Stanley
Oak Ridge National Laboratory


Dr. Andy Stephen, Biochemistry and Biophysics Group Lead

For more information, contact the RAS Biochemistry and Biophysics Group team lead:

Dr. Andy Stephen

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