Activation of Ras and its downstream extracellular signal-regulated protein kinases by the CDC25 homology domain of mouse Son-of-sevenless 1 (mSos1)

Kim, Jae Hoon; Shirouzu, Mikako; Kataoka, Tohru; Bowtell, David D.; Yokoyama, Shigeyuki

doi:10.1038/sj.onc.1201822

Cited by 16 publications

(21 citation statements)

References 21 publications

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“…The DH-PH unit is located so as to block the allosteric Ras-binding site in the catalytic domain (6). The fact that the catalytic domain is inactive without Ras bound to the allosteric site, combined with the blockage of the allosteric site by the DH-PH unit, explains the autoinhibition of constructs of SOS that include the DH-PH unit (7)(8)(9). These results do not, however, provide an explanation for how the blockage of the critical allosteric Ras-binding site by the DH-PH unit is alleviated during the activation of SOS.…”

mentioning

confidence: 99%

Computational docking and solution x-ray scattering predict a membrane-interacting role for the histone domain of the Ras activator son of sevenless

Sondermann

Nagar

Bar–Sagi

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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The Ras-specific nucleotide exchange factor son of sevenless (SOS) is a large, multidomain protein with complex regulation, including a Ras-dependent allosteric mechanism. The N-terminal segment of SOS, the histone domain, contains two histone folds, which is highly unusual for a cytoplasmic protein. Using a combination of computational docking, small-angle x-ray scattering, mutagenesis, and calorimetry, we show that the histone domain folds into the rest of SOS and docks onto a helical linker that connects the pleckstrin-homology (PH) and Dbl-homology (DH) domains of SOS to the catalytic domain. In this model, a positively charged surface region on the histone domain is positioned so as to provide a fourth potential anchorage site on the membrane for SOS in addition to the PH domain, the allosteric Ras molecule, and the C-terminal adapter-binding site. The histone domain in SOS interacts with the helical linker, using a region of the surface that in nucleosomes is involved in histone tetramerization. Adjacent surface elements on the histone domain that correspond to the DNA-binding surface of nucleosomes form the predicted interaction site with the membrane. The orientation and position of the histone domain in the SOS model implicates it as a potential mediator of membrane-dependent activation signals.histone fold ͉ membrane interaction ͉ small-angle x-ray scattering ͉ signal transduction ͉ structure T he small G protein Ras is a cellular switch that cycles between an active GTP-bound state and an inactive GDP-bound state. GTP and GDP are both slow to dissociate from Ras, and the action of nucleotide exchange factors is critical for converting inactive Ras⅐GDP to the active Ras⅐GTP form (1). The activation of growth factor receptors in animal cell signaling results in the recruitment of the Ras-specific nucleotide exchange factor son of sevenless (SOS) to the plasma membrane, where it engages Ras and causes dissociation of bound nucleotide (2). The unregulated activation of Ras is a frequent hallmark of many cancers, a fact that underscores the importance of strict control of the nature of the nucleotide bound to Ras (3).SOS is a large protein (Ϸ1,300 residues; see Fig. 1 for a schematic diagram of its domain structure) that promotes nucleotide release by binding to Ras and opening up its active site (4). The Rem (Ras exchanger motif) and Cdc25 (named for the Ras activator protein in yeast) domains, located in the C-terminal half of SOS, are the minimal elements required for nucleotide exchange activity. The catalytic site of SOS, where nucleotide release from Ras occurs, is located entirely within the Cdc25 domain (4).We recently made the surprising discovery that Ras, which is the substrate of SOS, is itself required for SOS activity (5, 6). The binding of Ras⅐GTP to a distal site on the Cdc25 domain, bracketed by the Rem domain, stimulates nucleotide exchange activity. Perhaps more surprising was the realization that the binding of Ras⅐GDP to the distal allosteric site is required even for basal SOS activit...

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confidence: 99%

Computational docking and solution x-ray scattering predict a membrane-interacting role for the histone domain of the Ras activator son of sevenless

Sondermann

Nagar

Bar–Sagi

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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“…1a) (13,14). In addition, Sos requires allosteric activation through a second Ras-binding site that bridges the Rem and Cdc25 domains (Fig.…”

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confidence: 99%

A Ras-induced conformational switch in the Ras activator Son of sevenless

Freedman

Sondermann

Friedland

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

133

152

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The Ras-specific guanine nucleotide-exchange factors Son of sevenless (Sos) and Ras guanine nucleotide-releasing factor 1 (RasGRF1) transduce extracellular stimuli into Ras activation by catalyzing the exchange of Ras-bound GDP for GTP. A truncated form of RasGRF1 containing only the core catalytic Cdc25 domain is sufficient for stimulating Ras nucleotide exchange, whereas the isolated Cdc25 domain of Sos is inactive. At a site distal to the catalytic site, nucleotide-bound Ras binds to Sos, making contacts with the Cdc25 domain and with a Ras exchanger motif (Rem) domain. This allosteric Ras binding stimulates nucleotide exchange by Sos, but the mechanism by which this stimulation occurs has not been defined. We present a crystal structure of the Rem and Cdc25 domains of Sos determined at 2.0-Å resolution in the absence of Ras. Differences between this structure and that of Sos bound to two Ras molecules show that allosteric activation of Sos by Ras occurs through a rotation of the Rem domain that is coupled to a rotation of a helical hairpin at the Sos catalytic site. This motion relieves steric occlusion of the catalytic site, allowing substrate Ras binding and nucleotide exchange. A structure of the isolated RasGRF1 Cdc25 domain determined at 2.2-Å resolution, combined with computational analyses, suggests that the Cdc25 domain of RasGRF1 is able to maintain an active conformation in isolation because the helical hairpin has strengthened interactions with the Cdc25 domain core. These results indicate that RasGRF1 lacks the allosteric activation switch that is crucial for Sos activity.Cdc25 ͉ nucleotide-exchange factor ͉ crystal structure ͉ Ras exchanger motif (Rem) domain ͉ Ras guanine nucleotide-releasing factor 1

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“…Structural [6,7] and biochemical [9,10] data showed that the catalytic activity of the Ras-GEF core of hSos1 (residues 742-1024) is modulated by an upstream REM domain. The novelty of this paper is to show that in order to maintain catalytic activity, interaction of the REM core with F577 is required, since the Sos Cat_F577A mutant shows reduced ability to catalyze guanine nucleotide dissociation and exchange on Ras in vitro and is strongly defective in activation of Ras signalling in vivo.…”

Section: Discussionmentioning

confidence: 99%

“…Mm quite precisely corresponds to the minimal functional domain [23], the minimal catalytic domain of hSos1 is larger [10]. Thus, it was of interest to accurately map the minimal catalytic region of hSos1 in order to highlight the structural features responsible for this difference.…”

Section: Minimal Ras-gef Functional Region Of Hsos1mentioning

confidence: 99%

“…The REM core, composed of helices a1, a2, a3, plays a key role in stabilizing the HI hairpin, since it forms a hydrophobic pocket (residues V606; L609; F623; T626; F627; T630; F634) that accommodates residues, I956 and F958, present on the hairpin structure [6]. Disruption of critical contacts between the REM domain and the catalytic core decreases hSos1 catalytic activity in vitro [9,10]. The REM domain contains a second binding site for nucleotidebound Ras, that hence acts not only as substrate but as a positive allosteric modulator as well [7].…”

Section: Introductionmentioning

confidence: 99%

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Catalytic competence of the Ras–GEF domain of hSos1 requires intra‐REM domain interactions mediated by Phenylalanine 577

et al. 2006

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The Ras-specific guanine nucleotide exchange region of hSos1 consists of two consecutive domains: the catalytic core (residues 742-1024) contains all residues binding to Ras, including the catalytic hairpin, and an upstream REM domain (residues 553-741), so called because it contains an evolutionary conserved Ras Exchange Motif (REM). We functionally define the boundaries of the REM domain through a combination of in vivo and in vitro assays. We show that an intra-REM domain interaction, mediated by phenylalanine 577, is required to allow interaction of the REM domain with the catalytic core, constraining it in the active conformation.

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Activation of Ras and its downstream extracellular signal-regulated protein kinases by the CDC25 homology domain of mouse Son-of-sevenless 1 (mSos1)

Cited by 16 publications

References 21 publications

Computational docking and solution x-ray scattering predict a membrane-interacting role for the histone domain of the Ras activator son of sevenless

Computational docking and solution x-ray scattering predict a membrane-interacting role for the histone domain of the Ras activator son of sevenless

A Ras-induced conformational switch in the Ras activator Son of sevenless

Catalytic competence of the Ras–GEF domain of hSos1 requires intra‐REM domain interactions mediated by Phenylalanine 577

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