Apparatus of Golgi - SpeedyLook encyclopedia

Discovered

The apparatus of Golgi was described by Camillo Golgi in 1898. It then observed a particular arrangement of the internal réticulé apparatus. It named this arrangement in the shape of crescent the dictyosome, which will be renamed later with its name, because of the importance of its work. Its research at the time raised much controversies. The coloring which it used to see the réticulé apparatus was coloring with the money. This method being not very specific let accept the scientific community that the dictyosomes were simply artefacts.

composition

The apparatus of Golgi is a cellular Organite consisted of one or more Dictyosome S, stacking of saccules membrane of form discoïdale and a network of canaliculi called network trans-golgien (Trans Golgi Network or TGN). Each dictyosome can be divided into three different functional areas: them saccules of the face cis or face of entry of the material of the endoplasmic Reticulum. them saccules of the median area. them saccules of the trans face or face of exit. The various parts of the apparatus of golgi are identified by the following dyes: the Tétraoxyde of osmium colors the golgi-cis, the dinucléoside diphosphatase colors thetrans one and acid phosphatase colors the network trans golgien.

Operation

The apparatus of Golgi is the place where some Protéine S are modified, in particular by Glycosylation, after their synthesis in the reticulum during the translation of the molecules of ARNm- and the assembly of the Protéoglycane S. The evolution of made up contained in the Dictyosome is carried out face cis (cis-Golgi, containing protein 60%, 40% of lipids) with the trans face (trans-Golgi, containing protein 70%, 30% of lipids) of this one. The proteins which compose each area are different. A retrograde flow is ensured to bring back all the proteins which were captured inopportunely in blisters COP I moving towards the trans face.

The function

One of the important roles of the apparatus of Golgi is related to phenomena of Endocytose. It is the point of required passage and traffic controller vésiculaire. It controls the number of Vésicule S going to the membrane and takes part in the membrane renewal. It involves post-traductionnelles modifications of the Protéines:

polypeptide cleavage of the precursors : maturation of the proteins
Glycosylation (addition of glucidic chains)
Sulphating
Phosphorylation

Post-traductionnelles modifications carried out in the apparatus of Golgi are essential with the correct addressing of proteins in the cell. For example, in the cis-Golgi, there is Phosphorylation certain residues mannose of dependant oligosaccharidic N chains on the proteins which end in the presence of mannose-6-phosphate. In the transone, receivers with mannose-6-phosphate thus concentrate proteins with mannose-6-phosphate in specific blisters which are then addressed to the Lysosome S. the proteins addressed to the Lysosome S are often dangeureuses lytic enzymes for the cell and its environment, them " signalement" by mannose-6-phosphate in the apparatus of Golgi prevents that they are excreted and destroy fabrics.

The segregation of proteins

The apparatus of Golgi ensures an accurate check on the proteins which leave it. Initially, it makes sure that the proteins necessary to the operation of the endoplasmic Réticulum will be turned over by a retrograde flow towards this last. These proteins are marked by sequence KDEL or KKXX according to their function. The KDEL corresponds to soluble proteins and the KKXX with membrane proteins. Certain proteins comprising sequence KKXX are used as receivers to the KDEL and thus ensure the retrograde flow of proteins KDEL of the golgi towards the endoplasmic Réticulum.

Then, there exist two types of secretions for proteins in Golgi. Constitutive secretion is generally directed towards the plasmic membrane. This secretion does not require any signal. Controlled secretion, as its name indicates it, requires a signal. This principle makes it possible to control the export of these proteins.

Simple: Golgi complex

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