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2ii0, resolution 2.02Å ()
Gene: SOS1 (Homo sapiens)
Related: 1bkd, 1nvv
Resources: FirstGlance, OCA, RCSB, PDBsum
Coordinates: save as pdb, mmCIF, xml


Crystal Structure of catalytic domain of Son of sevenless (Rem-Cdc25) in the absence of Ras

Publication Abstract from PubMed

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-A 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-A 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.

A Ras-induced conformational switch in the Ras activator Son of sevenless., Freedman TS, Sondermann H, Friedland GD, Kortemme T, Bar-Sagi D, Marqusee S, Kuriyan J, Proc Natl Acad Sci U S A. 2006 Nov 7;103(45):16692-7. Epub 2006 Oct 30. PMID:17075039

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.


[SOS1_HUMAN] Defects in SOS1 are the cause of gingival fibromatosis 1 (GGF1) [MIM:135300]; also known as GINGF1. Gingival fibromatosis is a rare overgrowth condition characterized by a benign, slowly progressive, nonhemorrhagic, fibrous enlargement of maxillary and mandibular keratinized gingiva. GGF1 is usually transmitted as an autosomal dominant trait, although sporadic cases are common.[1] Defects in SOS1 are the cause of Noonan syndrome type 4 (NS4) [MIM:610733]. NS4 is an autosomal dominant disorder characterized by dysmorphic facial features, short stature, hypertelorism, cardiac anomalies, deafness, motor delay, and a bleeding diathesis. It is a genetically heterogeneous and relatively common syndrome, with an estimated incidence of 1 in 1000-2500 live births. Rarely, NS4 is associated with juvenile myelomonocytic leukemia (JMML). SOS1 mutations engender a high prevalence of pulmonary valve disease; atrial septal defects are less common.[2][3][4][5][6][7][8][9]


[SOS1_HUMAN] Promotes the exchange of Ras-bound GDP by GTP.

About this Structure

2ii0 is a 1 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA.


  • Freedman TS, Sondermann H, Friedland GD, Kortemme T, Bar-Sagi D, Marqusee S, Kuriyan J. A Ras-induced conformational switch in the Ras activator Son of sevenless. Proc Natl Acad Sci U S A. 2006 Nov 7;103(45):16692-7. Epub 2006 Oct 30. PMID:17075039
  1. Hart TC, Zhang Y, Gorry MC, Hart PS, Cooper M, Marazita ML, Marks JM, Cortelli JR, Pallos D. A mutation in the SOS1 gene causes hereditary gingival fibromatosis type 1. Am J Hum Genet. 2002 Apr;70(4):943-54. Epub 2002 Feb 26. PMID:11868160 doi:S0002-9297(07)60301-2
  2. Roberts AE, Araki T, Swanson KD, Montgomery KT, Schiripo TA, Joshi VA, Li L, Yassin Y, Tamburino AM, Neel BG, Kucherlapati RS. Germline gain-of-function mutations in SOS1 cause Noonan syndrome. Nat Genet. 2007 Jan;39(1):70-4. Epub 2006 Dec 3. PMID:17143285 doi:ng1926
  3. Tartaglia M, Pennacchio LA, Zhao C, Yadav KK, Fodale V, Sarkozy A, Pandit B, Oishi K, Martinelli S, Schackwitz W, Ustaszewska A, Martin J, Bristow J, Carta C, Lepri F, Neri C, Vasta I, Gibson K, Curry CJ, Siguero JP, Digilio MC, Zampino G, Dallapiccola B, Bar-Sagi D, Gelb BD. Gain-of-function SOS1 mutations cause a distinctive form of Noonan syndrome. Nat Genet. 2007 Jan;39(1):75-9. Epub 2006 Dec 13. PMID:17143282 doi:10.1038/ng1939
  4. Ko JM, Kim JM, Kim GH, Yoo HW. PTPN11, SOS1, KRAS, and RAF1 gene analysis, and genotype-phenotype correlation in Korean patients with Noonan syndrome. J Hum Genet. 2008;53(11-12):999-1006. doi: 10.1007/s10038-008-0343-6. Epub 2008, Nov 20. PMID:19020799 doi:10.1007/s10038-008-0343-6
  5. Hanna N, Parfait B, Talaat IM, Vidaud M, Elsedfy HH. SOS1: a new player in the Noonan-like/multiple giant cell lesion syndrome. Clin Genet. 2009 Jun;75(6):568-71. doi: 10.1111/j.1399-0004.2009.01149.x. Epub, 2009 May 5. PMID:19438935 doi:10.1111/j.1399-0004.2009.01149.x
  6. Longoni M, Moncini S, Cisternino M, Morella IM, Ferraiuolo S, Russo S, Mannarino S, Brazzelli V, Coi P, Zippel R, Venturin M, Riva P. Noonan syndrome associated with both a new Jnk-activating familial SOS1 and a de novo RAF1 mutations. Am J Med Genet A. 2010 Sep;152A(9):2176-84. doi: 10.1002/ajmg.a.33564. PMID:20683980 doi:10.1002/ajmg.a.33564
  7. Fabretto A, Kutsche K, Harmsen MB, Demarini S, Gasparini P, Fertz MC, Zenker M. Two cases of Noonan syndrome with severe respiratory and gastroenteral involvement and the SOS1 mutation F623I. Eur J Med Genet. 2010 Sep-Oct;53(5):322-4. doi: 10.1016/j.ejmg.2010.07.011. Epub , 2010 Jul 29. PMID:20673819 doi:10.1016/j.ejmg.2010.07.011
  8. Denayer E, Devriendt K, de Ravel T, Van Buggenhout G, Smeets E, Francois I, Sznajer Y, Craen M, Leventopoulos G, Mutesa L, Vandecasseye W, Massa G, Kayserili H, Sciot R, Fryns JP, Legius E. Tumor spectrum in children with Noonan syndrome and SOS1 or RAF1 mutations. Genes Chromosomes Cancer. 2010 Mar;49(3):242-52. doi: 10.1002/gcc.20735. PMID:19953625 doi:10.1002/gcc.20735
  9. Lepri F, De Luca A, Stella L, Rossi C, Baldassarre G, Pantaleoni F, Cordeddu V, Williams BJ, Dentici ML, Caputo V, Venanzi S, Bonaguro M, Kavamura I, Faienza MF, Pilotta A, Stanzial F, Faravelli F, Gabrielli O, Marino B, Neri G, Silengo MC, Ferrero GB, Torrrente I, Selicorni A, Mazzanti L, Digilio MC, Zampino G, Dallapiccola B, Gelb BD, Tartaglia M. SOS1 mutations in Noonan syndrome: molecular spectrum, structural insights on pathogenic effects, and genotype-phenotype correlations. Hum Mutat. 2011 Jul;32(7):760-72. doi: 10.1002/humu.21492. Epub 2011 Apr 28. PMID:21387466 doi:10.1002/humu.21492

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