MCDB 418 Lecture Notes - Lecture 16: P53, Apoptosis, Microtubule
2 Apr 2017
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Small g proteins g protein are molecular switches with a built in automatic timer. When bound ot gdp, the switch is off . When bound to gtp, switch is on . G protein itself is a gtpase (inefficient one) , it"ll eventually hydrolyze the bound gtp and turn the switch off. Unlike large proteins (trimers), small g proteins have molecular weights around 20 kda/exist as either monomer or homoligomers. Most small g proteins are structurally related to ras. Most small g proteins are covalently attached by lipids. Small g proteins require gtpase-activating protein (gap) for its gtpase activity. Ras is a 21 kda g protein that form homo-dimers. In mammals, ras associated with activation of raf + its downstream signal transducers. Mammalian rasgap: 120 kda; can gtpase activity of ras by 100-fold. Guanine nucleotide exchange factors (gefs): proteins/protein domains involved in activation of ras. This family of proteins involved in cytoskeleton reorganization, membrane ruffling, and cell migration.
