[[Signal Transduction]] - [[Cell Surface Receptor]]
Bind to extracellular domains of transmembrane receptors that have kinase domains
==Regulate the control of growth==
==Receptor Tyrosine Kinase==
====Function/Purpose:====
Phosphorylates proteins on the hydroxyl group of tyrosine residues
====Components:====
*Adaptor Protein - Grb-2
**Links phosphorylation to stimulation of cell gorowth
*Phosphorylation allows the Grb-2 to bind to the phospohtyrosine residues in the receptor tyrosine kinase
*Protein SOS/Guanine-nucleotide Exchange Facgtor (GEF) binds to RAS and activates it
**Reaches the nucleotide binding pocket and opens it up so that GDP can escape and GTP can enter in its place
*RAS is activated and binds to other components of the molecular circuitry leading to more activation of other protein kinases with a similar phospohrylation for cell growth
*RAS is just like [[G Protein]]alpha that is GDP which becomes GTP through the oxidation of a GTP or creates an exchange of GTP
*RAS also has an intrinsic GTPase activity
**GTPase activity is slow but is augmented by helper proteins - GTPase activating proteins (GAPs)
====Small G proteins or small GTPases====
*RAS regulates cell growth through SER and THR protein kinases
*Rho reorganizes cytoskeleton through SER and THR protein kinases
*Arf activates ADP-ribosyltransferase of cholera toxin A1 subunit, regulates vesicular trafficking pathways, activates phospholipase D
*Rab key role in secretory and endocytotic pathways
*Ran transport RNA and protein into and out of the nucleus
====Salient Example:====
Epidermal Growth Factor bind to Epidermal Growth Factor receptor
Binding in extracellular domain causes receptor dimerization and undergoes cross phosphorylation and activation
====Additional Information:====
