 The study of proteins in vivo is often concerned with the synthesis and localization of the protein within the cell . Although many intracellular proteins are synthesized in the cytoplasm and membrane @-@ bound or <unk> proteins in the <unk> <unk> , the specifics of how proteins are targeted to specific organelles or cellular structures is often unclear . A useful technique for assessing cellular localization uses genetic engineering to express in a cell a fusion protein or <unk> consisting of the natural protein of interest linked to a " reporter " such as green fluorescent protein ( <unk> ) . The fused protein 's position within the cell can be cleanly and efficiently visualized using microscopy , as shown in the figure opposite . 
