Describe protein targetting to chloroplast.
Answers
Targeting signals are the pieces of information that enable the cellular transport machinery to correctly position a protein inside or outside the cell. This 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 or targeting peptides. There are two types of targeting peptides, the presequences and the internal targeting peptides. The presequences of the targeting peptide are often found at the N-terminal extension and is composed of between 6-136 basic and hydrophobic amino acids. In case of peroxisomes the targeting sequence is on the C-terminal extension mostly. Other signals, known as signal patches, are composed of parts which are separate in the primary sequence. They become functional when folding brings them together on the protein surface. In addition, protein modifications like glycosylations can induce targeting.
Mitochondrial, chloroplast, and nuclear targeting are generally similar to peroxisomal targeting. That is, a certain amino acid sequence sends the protein to its target organelle