User:Jeremy Chieh-Yu Chung/Sandbox 1
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(New page: =='''RAS PROTEIN'''== ---- ===INTRODUCTION=== Ras protein belongs to the super-family known as "low-molecular weight G-proteins." They are distinct from heterotrimeric G-protien. The guan...)
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Revision as of 16:31, 9 April 2011
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RAS PROTEIN
INTRODUCTION
Ras protein belongs to the super-family known as "low-molecular weight G-proteins." They are distinct from heterotrimeric G-protien. The guanine nucleotide is the binding site for GTP and GDP, and the binding of either molecule is governed by GTPase.
HISTORY
RAS protein was first identified to be responsible for cancer causing activities. It was first found in rats, hence the name Rat sarcoma. It was once thought to act only at plasma membrane, but later research showed that it has signal transduction ability.
STRUCTURE
RAS protein is a monomeric globular protein with 189 amino acid residues. Its secondary structure consists six stranded beta sheet and five alpha helices. The G domain of the protein binds to guanosine nucleotides, and it has five motifs that bind to either GTP or GDP. The C terminal is the membrane targeting region.
FUNCTION
The binary switches, which is controlled by an exchange factor, govern intracellular signal transduction. When bound to GDP, RAS is in the inactive state. RAS is in the active state when GTP is bound. RAS protein is crucial in proliferation, adhesion and apoptosis.
ACTIVATION
The activation of Ras signaling leads to cellular differentiation, growth and survival. Its receptor is located in the cell membrane, and its action is regulated by exchange factors and GAP, which catalyzes the hydrolysis of GTP.
MUTATION
RAS protein, when mutated, results in permanent activation of Ras signaling even in the absence of extracellular signals/ growth factors
