Ras Interaction with Two Distinct Binding Domains in Raf-1 5 Be Required for Ras Transformation

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  • Drugan, Jonelle K.
    • University of North Carolina at Chapel Hill
  • Khosravi-Far, Roya
    • University of North Carolina at Chapel Hill
  • White, Michael A.
    • Other Affiliation: Cold Spring Harbor Laboratory
  • Der, Channing J.
    • University of North Carolina at Chapel Hill
  • Sung, Ying Ju
    • Other Affiliation: New York State Institute for Basic Research in Developmental Disabilities
  • Hwan, Yu Wen
    • Other Affiliation: New York State Institute for Basic Research in Developmental Disabilities
  • Campbell, Sharon L.
    • University of North Carolina at Chapel Hill
Abstract
  • Although Raf-1 is a critical Ras effector target, how Ras mediates Raf-1 activation remains unresolved. Raf-1 residues 55-131 define a Ras-binding domain essential for Raf-1 activation. Therefore, our identification of a second Ras-binding site in the Raf-1 cysteine-rich domain (residues 139-184) was unexpected and suggested a more complex role for Ras in Raf-1 activation. Both Ras recognition domains preferentially associate with Ras-GTP. Therefore, mutations that impair Ras activity by perturbing regions that distinguish Ras-GDP from Ras-GTP (switch I and II) may disrupt interactions with either Raf-1-binding domain. We observed that mutations of Ras that impaired Ras transformation by perturbing its switch I (T35A and E37G) or switch II (G60A and Y64W) domain preferentially diminished binding to Raf-1-(55-131) or the Raf-1 cysteine-rich domain, respectively. Thus, these Ras-binding domains recognize distinct Ras-GTP determinants, and both may be essential for Ras transforming activity. Finally, since Ha-Ras T35A and E37G mutations prevent Ras interaction with full-length Raf-1, we suggest that Raf-Cys is a cryptic binding site that is unmasked upon Ras interaction with Raf-1-(55-131).
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  • Article
Rights statement
  • In Copyright
Journal title
  • The Journal of Biological Chemistry
Journal volume
  • 271
Journal issue
  • 1
Page start
  • 233
Page end
  • 237
Language
  • English
ISSN
  • 0021-9258
  • 1083-351X

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