Question

· Discuss protein targeting in cells.

Answer 1

Protein Targeting (Paotein sorting or protein tarrgeting ) It is a biological process in which proteins are transported to different locations inside the cell oY outside the cell. Proteins has to be localized correctly perform function, Paoteins are synthesized either in cytosol or in the to gardancod endoplasmic reticulum. Some cytoplasmic proteins are targeted to a parbiuilar site because they may contain some specific amino atid sequence which causes them to bind to receptors located at that site. vom Many proteins are ambedded with or associated with membranes. In eukanyotic cells, membranes form boundaries urth tompantments including nucleus, mitochondria , endoplasmic rehiculum and golgi complex: 2i Usually proteins are synthesised in cytosol and are then modified coth lipid anchor. Paoteins that are targeted into intracellular membranes require sorting signals that direct their transport from cy tosol. Proteins localized within membranes which are involved in endocytosis and exocytosis are finst targeted to ehdo plasmic which then use membrane transport pathways to reticulum , reach other destinations. Targeting of proteins to ER begins before the poly peptide chain Is completely synthesized. variety of mechanisms to From ER protelns uses a reach different compartments . Som e proteins simply diffise and stick in nucelear envelope, since it is direct continuity weth ER.

If the proteins has to membrane , endosomes and lysosomes, they must enter the secreto ry pathway and use membrane tvafficking pathways Many membyane proteins are divected to specific pathuays to reach specific organelles (usually secre tory and endoytic pathuky) since they con tain specific sovting signals in ytoplasmic tails which funclions as zip codes. reach golgi compler, plasma