Small G proteins GTPases

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B-Ras1
B-Ras1
 
B-Ras2
B-Ras2
Small G proteins (GTPases)
There are five major families of small GTPases
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Functions Ras , Rho
Family Signaling Rab Family Vesicle
Trafficking (Targeting, Docking, Fusion) Arf
Family Vesicle Trafficking (Budding) Ran
Nuclear Import
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Structure of Small G proteins
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The C-terminal region of small GTPases is
post-translationally modified with lipids
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Small G proteins function as Molecular Switches
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The Ras Signaling Pathway
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Exchange Factors (GEF) are constitutively active
and are recruited to the appropriate site to
have their effects
Contd from 2
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GTPase Activating Proteins (GAPs)
Small GTPases have very low GTPase activity GAPs
increase catalytic activity by about a 1000 fold
GAPs contribute a catalytic Arg to form the
transition state. Different G proteins have
specific GAPs
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The Ras pathway for Gene Expression
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The Rho/Rac /CDc42 pathway for Cytoskeletal
Reorganization
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Regulators of Rho/Rac/Cdc42
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Rabs and Vesicle Trafficking
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Cyclical activation and Inactivation of Rab and
Translocation
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Ran and Nuclear Import/Export Cycle
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Export Cycle for Ran
exportin
RNA

RNA

RNA

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Small G protein Regulation of Protein Synthesis
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Two types of Regulation by G proteins