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G proteins, effectors and GAPs: structure and mechanism
1Howard Hughes Medical Institute, University of Texas, Southwestern Medical Center, Dallas 75235-9050, USA. sprang@howie.swmed.edu
Current Opinion in Structural Biology
|January 22, 1998
Summary
G proteins are regulatory GTPases that activate effectors when bound to GTP. Structural studies reveal how G proteins achieve specificity and how GTPase-activating proteins stimulate GTP hydrolysis.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- G proteins are key regulators of cellular signaling pathways.
- Their function relies on the binding and hydrolysis of guanosine triphosphate (GTP).
- Understanding G protein-effector interactions is crucial for deciphering cellular communication.
Purpose of the Study:
- To elucidate the structural mechanisms underlying G protein-effector complex formation.
- To investigate how GTP binding is coupled to effector activation.
- To explore the common principles of GTPase-activating protein (GAP)-mediated GTP hydrolysis stimulation.
Main Methods:
- X-ray crystallography was used to determine the structures of G protein-effector complexes.
- Structural analysis focused on Ras homologs and their effector domains.
- Complexes of G proteins with structurally diverse GTPase-activating proteins were also studied.
Main Results:
- Structures revealed how G proteins bind and activate downstream effectors in their GTP-bound state.
- Specific interactions between G protein switch regions and effector domains dictate specificity.
- Common mechanisms for GTP hydrolysis stimulation by GAPs involve direct interactions with labile G protein switch regions.
Conclusions:
- G protein-effector interactions are structurally diverse yet follow conserved principles.
- G protein specificity is achieved through precise molecular recognition.
- GTPase-activating proteins utilize conserved mechanisms to enhance GTP hydrolysis, terminating the signal.