Correlation between self-association modes and GTPase activation of dynamin

Area of Science:

• Molecular and Cell Biology
• Biochemistry
• Cellular Dynamics

Background:

• Dynamin's GTPase activity is crucial for clathrin-coated vesicle internalization.
• Dynamin self-assembly (oligomerization) is thought to mediate its mechanical and enzymatic functions.
• The precise mechanism coupling dynamin's GTPase activity to vesicle internalization remains unclear.

Purpose of the Study:

• To investigate the equilibrium dynamics of dynamin self-assembly.
• To characterize the kinetics of GTP and GDP binding to dynamin.
• To explore the relationship between dynamin oligomerization and GTPase activation, particularly on microtubule lattices.

Main Methods:

• Stopped-flow fluorescence spectroscopy to measure binding kinetics.
• Analysis of tetramer/monomer equilibrium.
• Experiments demonstrating cooperativity of binding and GTPase activation on microtubules.

Main Results:

• Dynamin exhibits a tetramer/monomer equilibrium with a specific equilibrium constant.
• Rate constants for the association and dissociation of mantGTP and mantGDP were determined.
• Dynamin binding and GTPase activation show cooperativity on microtubules.

Conclusions:

• Dynamin self-assembly is necessary but not sufficient for maximal GTPase activity.
• Proper conformation or orientation of dynamin molecules within an oligomer is required for full enzymatic function.
• These findings provide insights into the regulation of dynamin's role in endocytosis.