Room For Error In Secretory Pathways
...from a cell into the extracellular environment. It involves the journey of the protein that is destined to be secreted, from the ribosomes on the rough endoplasmic reticulum to the various compartments of the Golgi apparatus, packaged into a vesicle and finally secreted by exocytosis, via fusion with the plasma membrane. Each step in the pathway has factors determining the passage of the protein such as measures of transport regulation that signal protein location, the mechanics of proceeding further in the pathway, selection of proteins or modifications of the protein itself. Each of these factors contributes to the arrival and final structure of the secreted protein. In reference to error in the secretory pathway, there is extremely little room for any, as correct sorting and packaging is so crucial that mistakes lead to fatal and severe diseases. This essay will this outline the main stages of the secretory pathway, the levels of regulation and the consequences of error in the secretory pathway which will illustrate that there is minimal room for mistakes in this process.
Protein targeting or protein sorting is the mechanism by which cells transport proteins to the appropriate positions in the cell or outside of it. Sorting targets can be the inner space of an organelle, any of several interior membranes, the cell's outer membrane or its exterior via secretion. The delivery process is carried out based on information contained in the protein itself. This 'information' is coded as targeting signals which enable the cellular transport machinery to correctly position a protein inside or outside the cell. The information is contained in the polypeptide chain or in the folded protein. The continuous stretch of amino acid residues in the chain that enables targeting are called signal peptides. This short amino acid sequence functions as a postal code for the...
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