For how many proteins were targeted therapeutics initially conceived ?
Some transferred chloroplast DNA protein products get directed to the secretory pathway ( though it should be noted that many secondary plastids are bounded by an outermost membrane derived from the host 's cell membrane , and therefore topologically outside of the cell , because to reach the chloroplast from the cytosol , you have to cross the cell membrane , just like if you were headed for the extracellular space .