Sandbox8999: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 6: | Line 6: | ||
An individual clathrin molecule is composed of three heavy chains, each being attached to a light chain. This structure is often referred to as a triskelion shape.<ref name="harrison" /> The heavy chains of clathrin are made of an amino-terminal, a beta-propellor domain containing multiple repeats of the WD40 binding motif, alpha-helical zig-zags close to 30 amino acids in length, a lengthened alpha-helix where the threefold contacts, and a carboxy-terminal.<ref name="harrison" /> The aforementioned zig-zags are what create the “leg” looking structure of the triskelion.<ref name="harrison" /> Part of the heavy chain is designated to bind to the light chains, of which there are two variations in mammals. The heavy chain and light chain bind through one long alpha helix towards the center of the protein.<ref name="harrison" /> | An individual clathrin molecule is composed of three heavy chains, each being attached to a light chain. This structure is often referred to as a triskelion shape.<ref name="harrison" /> The heavy chains of clathrin are made of an amino-terminal, a beta-propellor domain containing multiple repeats of the WD40 binding motif, alpha-helical zig-zags close to 30 amino acids in length, a lengthened alpha-helix where the threefold contacts, and a carboxy-terminal.<ref name="harrison" /> The aforementioned zig-zags are what create the “leg” looking structure of the triskelion.<ref name="harrison" /> Part of the heavy chain is designated to bind to the light chains, of which there are two variations in mammals. The heavy chain and light chain bind through one long alpha helix towards the center of the protein.<ref name="harrison" /> | ||
[[Image:LatticeStructure.png |frame| a) Clathrin monomer with labeled heavy and light chains b) Clathrin monomers forming a basic lattice structure. Clathrin is made of individual triskelion components that come together to form the cage-like structure of clathrin. Each vertex is composed of a triskelion leg. Although there are various packing models for clathrin cage assembly, the overall theme is multiple triskelions coming together to form the cage like structure.<ref name=" | [[Image:LatticeStructure.png |frame| a) Clathrin monomer with labeled heavy and light chains b) Clathrin monomers forming a basic lattice structure.<ref name="pearse">PMID: 1063406</ref> Clathrin is made of individual triskelion components that come together to form the cage-like structure of clathrin.<ref name="crowther" /> Each vertex is composed of a triskelion leg.<ref name="crowther" /> Although there are various packing models for clathrin cage assembly, the overall theme is multiple triskelions coming together to form the cage like structure.<ref name="crowther" />]] | ||
===Lattice=== | ===Lattice=== | ||
| Line 12: | Line 12: | ||
Individual clathrin molecules can assemble into cage-like structures. When individual clathrin molecules come together, a lattice is formed where each lattice point is associated with the center of a triskelion (from the Greek word meaning “a three legged structure”).<ref name="harrison" /> According to Crowther, R.A., clathrin vesicles are constructed from 12 pentagonal units plus a number of hexagonal units, with the number of hexagons increasing for larger clathrin coats.<ref name="crowther">PMID: 7328122 </ref> The term “cage” can be used to refer to empty shells composed only of clathrin where “coat” refers to clathrin plus associated proteins and vesicles.<ref name="crowther" /> Clathrin lattices are formed under optimal conditions of physiological pH (6.0-6.5) and in the presence of Calcium or Magnesium ions.<ref name="crowther" /> Various packing models have been investigated as to how the individual triskelion legs assemble into clathrin cages.<ref name="crowther" /> As mentioned above, the center of the triskelion legs occurs at each vertex of the cage, meaning pentagons, heptagons, and hexagons can be formed.<ref name="crowther" /> In the individual triskelion legs, the bend in the leg is 160 Angstroms from the vertex, giving rise to two models of packing: simple side-by-side packing or a cross-over type of packing,<ref name="crowther" /> Cross-over packing occurs when a hexamer of triskelions are formed with crossing over of the leg portions of the triskelions.<ref name="crowther" /> Simple packing does not involve crossing over, but side by side packing of the leg portions of the triskelions.<ref name="crowther" /> | Individual clathrin molecules can assemble into cage-like structures. When individual clathrin molecules come together, a lattice is formed where each lattice point is associated with the center of a triskelion (from the Greek word meaning “a three legged structure”).<ref name="harrison" /> According to Crowther, R.A., clathrin vesicles are constructed from 12 pentagonal units plus a number of hexagonal units, with the number of hexagons increasing for larger clathrin coats.<ref name="crowther">PMID: 7328122 </ref> The term “cage” can be used to refer to empty shells composed only of clathrin where “coat” refers to clathrin plus associated proteins and vesicles.<ref name="crowther" /> Clathrin lattices are formed under optimal conditions of physiological pH (6.0-6.5) and in the presence of Calcium or Magnesium ions.<ref name="crowther" /> Various packing models have been investigated as to how the individual triskelion legs assemble into clathrin cages.<ref name="crowther" /> As mentioned above, the center of the triskelion legs occurs at each vertex of the cage, meaning pentagons, heptagons, and hexagons can be formed.<ref name="crowther" /> In the individual triskelion legs, the bend in the leg is 160 Angstroms from the vertex, giving rise to two models of packing: simple side-by-side packing or a cross-over type of packing,<ref name="crowther" /> Cross-over packing occurs when a hexamer of triskelions are formed with crossing over of the leg portions of the triskelions.<ref name="crowther" /> Simple packing does not involve crossing over, but side by side packing of the leg portions of the triskelions.<ref name="crowther" /> | ||
[[Image:LatticeStructure2.png |frame| Models of the various packing models of triskelion components of clathrin. Each vertex of the polygon is made of a triskelion and the legs of the triskelion run along the edges. (a) Simple side-by-side packing model of the legs in which there is no overlap and a hexamer is formed. (b) Model of cross-over packing of the triskelion legs forming a hexamer and (c) Similar model as (b) except a pentamer is formed by the triskelions with crossing over of the leg portions.<ref name="crowther" />]] | [[Image:LatticeStructure2.png |frame| Models of the various packing models of triskelion components of clathrin.<ref name="crowther" /> Each vertex of the polygon is made of a triskelion and the legs of the triskelion run along the edges. (a) Simple side-by-side packing model of the legs in which there is no overlap and a hexamer is formed. (b) Model of cross-over packing of the triskelion legs forming a hexamer and (c) Similar model as (b) except a pentamer is formed by the triskelions with crossing over of the leg portions.<ref name="crowther" />]] | ||
== Function == | == Function == | ||
