Intracellular protein transport

In the last chapter we have seen how proteins are inserted post-translationally into mitochondria. Similar pathways exist for plastids, nucleus and peroxisome, although the signal sequences and transport mechanism vary. In most cases the signal sequence is cleaved off after the protein has reached its destination, the exception are nuclear proteins because the nucleus breaks down during each cell cycle, releasing its proteins into the cytoplasm. Hence after each cell division nuclear proteins need to be reimported.

Insertion of proteins into the ER however occurs co-translationally, from there it is then transported by specialised vesicles to GoLGl-apparatus, lysosomes, endosomes, secretory vesicles and plasma membrane.

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