Sandbox Reserved 1495

From Proteopedia

proteopedia linkproteopedia link

Contents 1 Generalities 2 Function 3 Relevance 4 Structural highlights 5 References

Generalities

Clathrin is a 3 legged cytoplasmic protein with 3 heavy chains and 3 light chains. It has a triskelion shape (A tryskelion consists of three bent limbs radiating from a centre) and can self-assembled into a polyhedral structure arround [vesicles] of eukaryotic cells. Triskelia can polymerize into cages or even flat lattice, depending on the ratio hexagon/pentagon formed during the process.

spinqualitylabelsall models Insert caption here Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Function

Communication beetween the different compartiments of eukaryotic cell and plasma membrane is allowed by vesicles, which convey molecules (called cargos) within the cytoplasm. Clathrin are involved in the formation of those vesicles in a process named clathrin mediated endocytosis. However this process refers only to intake through vesicles from the plasma membrane. Clathrins form a skeleton around the vesicle once several triskelia are assembled. The coated vesicle like so formed will then lose its round protein skeleton after its departure from the initial compartment because the clathrin cage is quickly dismantled. This phenomena proceeds through five stages: initiation, cargo selection, coat assembly, scission and uncoating. During the cargo selection and the initiation, clathrins polymerize into hexagons and pentagons. The ratio between these two shapes dependents of the cells' curve.

Relevance

Endocytosis is essential to neurotransmission, as well to signal transduction and more generally to the regulation of many plasma membrane activities and is thus essential to eukaryotic life. Indeed, clathrins are shown as a active player in the recycling of synaptics vesicles, they are nessecaryl to the good functionement of synaptic transmission.

Structural highlights

To bind to the membrane or to cargo receptors clathrin adopt a basket shape, this is not spontaneous. This assembly nessecites adaptor proteins, complexes (such as AP2) and accessory proteins (such as AP180 and epsin). All of them are recruited by the plasma membrane. Adaptor proteins joined to the N-terminal β-propeller domain, with the help of arrestins and Hsc70, to the clathrin heavy chain.

</StructureSection>

References

Molecular mechanism and physiological functions of clathrin‑mediated endocytosisVOLUME 12 | AUGUST 2011 Harvey T. McMahon and Emmanuel Boucrot VOLUME 12 | AUGUST 2011