Protein targeting - how do you tell a protein where to go?

For the majority of proteins, synthesis begins in the cytoplasm but the proteins' final functional location could be at a range of sub-cellular locations. To enable the cell to target proteins to their final destinations, non-cytoplasmic; proteins contain a range of targeting Signals that function to direct them along a targeting pathway. Targeting signals may occur as a linear amino acid sequence but are dependent more often on the final three-dimensional geting fold of the protein, which exposes the signal to the targeting machinery via a secondary structure element or targeting patch. The process of protein targeting provides an ideal area to allow students to consider the dynamic and complex nature of cell biosynthesis, and allows educators to show how the physico-chemical properties of amino acids can be important in protein function at the primary, secondary, and tertiary levels.