Beschreibung:
<jats:p>We have recently found that ralGDS family members (RGL and ralGDS) are putative effector proteins of <jats:italic>ras</jats:italic> p21. <jats:italic>rap</jats:italic>1 p21 is a small GTP‐binding protein which has the same amino acid sequence as the effector loop of <jats:italic>ras</jats:italic> p21. We examined the effect of <jats:italic>rap</jats:italic>1 p21 on the interaction of <jats:italic>ras</jats:italic> p21 with RGL. The GTP‐bound form of <jats:italic>rap</jats:italic>1 p21 interacted with RGL as well as did <jats:italic>ras</jats:italic> p21. <jats:italic>rap</jats:italic>1 p21 inhibited the interaction of <jats:italic>ras</jats:italic> p21 with RGL. RGL was phosphorylated by cyclic AMP‐dependent protein kinase (protein kinase A). Phosphorylation of RGL did not affect its binding to <jats:italic>ras</jats:italic> p21 and <jats:italic>rap</jats:italic>1 p21 under the conditions that phosphorylation of Raf‐1 reduced its affinity for <jats:italic>ras</jats:italic> p21. These results demonstrate that <jats:italic>rap</jats:italic>1 p21 but not protein kinase A regulates the interaction of <jats:italic>ras</jats:italic> p21 with RGL and suggest that <jats:italic>rap</jats:italic>1 p21 and protein kinase A may cooperate to distinguish the signal of <jats:italic>ras</jats:italic> p21 to RGL from that to Raf‐1.</jats:p>