Ras‐interacting domain of RGL blocks Ras‐dependent signal transduction in Xenopus oocytes

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Abstract
RalGDS family members (RalGDS and RGL) interact with the GTP‐bound form of Ras through its effector loop. The C‐terminal region (amino acids 602–768) of RGL is responsible for binding to Ras. In this paper we characterized a Ras‐interacting domain of RGL using deletion mutants of RGL(602–768). RGL(602–768), RGL(632–768), and RGL(602–734) bound to the GTP‐bound form of Ras and inhibited the GAP activity of NF‐1. RGL(646–768) showed a low binding activity to Ras and inhibited GAP activity of NF‐1 weakly. None of RGL(659–768), RGL(685–768), RGL(602–709), and RGL(602–686) bound to Ras or inhibited GAP activity of NF‐1. These results indicate that amino acids 632–734 of RGL constitute a nearly minimal domain that contains the binding element for Ras. RGL(632–734) inhibited v‐Ras‐ but not progesterone‐induced Xenopus oocyte maturation. Furthermore, RGL(632–734) inhibited v‐Ras‐ but not v‐Raf‐dependent extracellular signal‐regulated kinase activation in Xenopus oocytes. These results clearly demonstrate that the Ras‐interacting domain of RGL is important for Ras‐dependent signal transduction in vivo.