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Interaction of a novel GDP exchange inhibitor with the Ras protein

A K Ganguly1, Y S Wang, B N Pramanik

  • 1Agouron Pharmaceuticals, San Diego, California 92121, USA.

Biochemistry
|December 8, 1998
PubMed

Insights

A novel inhibitor (SCH-54292) targets mutated Ras proteins, crucial in many cancers. Low magnesium reveals Ras protein conformational changes, enhancing inhibitor binding for potential cancer therapies.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Mutated Ras proteins are implicated in various human cancers.
  • Targeting Ras function with inhibitors offers a potential therapeutic strategy for Ras-related tumors.

Purpose of the Study:

  • To investigate the interaction between a novel GDP exchange inhibitor (SCH-54292) and the Ras-GDP protein.
  • To elucidate the conformational changes in Ras protein at low Mg2+ concentrations and their effect on inhibitor binding.

Main Methods:

  • Nuclear Magnetic Resonance (NMR) spectroscopy, specifically 2D 1H-15N HSQC experiments.
  • Studying the Ras-GDP protein in the presence of SCH-54292 and varying Mg2+ concentrations.
  • Deriving a structural model of the inhibitor-Ras-GDP complex using NOE distance constraints.

Main Results:

  • Inhibitor binding to Ras-GDP was enhanced at low Mg2+ concentrations, facilitating stable complex formation for NMR studies.
  • Ras protein exhibited two conformations in slow exchange at low Mg2+, involving the GDP binding pocket, switch I, and switch II regions.
  • These conformational changes were reversible upon addition of excess Mg2+.
  • The inhibitor was found to bind to the critical switch II region of the Ras protein.

Conclusions:

  • Low Mg2+ concentrations induce conformational changes in Ras protein, enhancing the binding of the SCH-54292 inhibitor.
  • The inhibitor targets the switch II region, a key area for Ras protein function.
  • Understanding these interactions provides insights for developing targeted therapies against Ras-driven cancers.

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