RASs
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The RAS gene family encodes membrane-associated, guanine nucleotide-binding proteins (GTPases) that are involved in the control of cellular proliferation and differentiation.
Similar to other guanine-binding proteins (such as the heterotrimeric G proteins), the RAS proteins cycle between an active guanosine-triphosphate (GTP) bound form and an inactive, guanosine-diphosphate (GDP) bound form.
The weak intrinsic GTPase activity of RAS proteins is greatly enhanced by the action of GTPase-activating proteins (GAPs). GAP is an effector of RAS oncogene action.
Function
RAS genes encode membrane-bound guanine nucleotide-binding proteins that function in the transduction of signals that control cell growth and differentiation.
Binding of GTP activates RAS proteins, and subsequent hydrolysis of the bound GTP to GDP and phosphate inactivates signaling by these proteins.
GTP binding can be catalyzed by guanine nucleotide exchange factors for RAS, and GTP hydrolysis can be accelerated by GTPase-activating proteins (GAPs).
The first exchange factor to be identified for RAS was the S. cerevisiae CDC25 gene product. Genetic analysis indicated that CDC25 is essential for activation of RAS proteins. In Drosophila, the protein encoded by the ?son of sevenless? gene (Sos) contains a domain that shows sequence similarity with the catalytic domain of CDC25. Sos may act as a positive regulator of RAS by promoting guanine nucleotide exchange.
Members
- H-ras (HRAS) (MIM.190020)
- Ki-ras (KRAS) (MIM.190070)
- N-ras (NRAS) (MIM.164790)
Rab (Rab GTPases)
Rho
Ral
RAF
Function
The Ras family of small G proteins, which includes H-ras, R-ras and Rap, are important elements in cellular signalling pathways that control integrin function.
See also
SOSs: SOS1
References
Parton RG, Hancock JF. Lipid rafts and plasma membrane microorganization: insights from Ras. Trends Cell Biol. 2004 Mar;14(3):141-7. PMID: 15003623
Malumbres M, Barbacid M. RAS oncogenes: the first 30 years. Nat Rev Cancer. 2003 Jun;3(6):459-65. PMID: 12778136
Shields JM, Pruitt K, McFall A, Shaub A, Der CJ. Understanding Ras: ?it ain?t over ?til it?s over?. Trends Cell Biol. 2000 Apr;10(4):147-54. PMID: 10740269
P.S.
Animation of the organisation and function of the Ras-Raf-MEK-ERK pathway at Expert Reviews in Molecular Medicine