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GTPase involved in endocytosis

General Information

Dynamin was discovered because of its binding to microtubules. It was later shown not to function in the cytoskeleton but in endocytosis. Dynamin is required for clathrin - mediated endocytosis. It contains a NH2 - terminal GTPase domain, a middle pleckstrin - homology domain, and a COOH- terminal proline - rich sequence. The COOH - terminal sequence binds to amphiphilin which contains a SH3 domain that recognizes the proline -rich sequence of dynamin. There are at least three isoforms of dynamin: Dynamin 1 is enriched in synapses whereas dynamin 2 is ubiquitous and dynamin 3 is expressed in the testis. Neuronal dynamin 1 is phosphorylated by protein kinase C and dephosphorylated by calcineurin during an action potential in the nerve terminal. It is possible that the dephosphorylation provides a trigger for endocytosis.
movie structure clathrin

dynamin ; What is it? a large GTPase involved in the scission of nascent vesicles from parent membranes.

How do we think it works? Dynamin forms a helix around the neck of a nascent vesicle (like in the above movie). Cooperative GTP hydrolysis results in the lengthwise extension of this helix, breaking the vesicle neck (but see below for an overview of other plausible mechanisms).

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TG lawen ?