In a compartmentalized cell, correct protein localization is crucial for function of virtually all cellular processes. From the cytoplasm as a starting point, proteins are imported into organelles by specific targeting signals. Many proteins, however, act in more than one cellular compartment. In this chapter, we discuss mechanisms by which proteins can be targeted to multiple organelles with a focus on a novel gene regulatory mechanism, functional translational readthrough, that permits multiple targeting of proteins to the peroxisome and other organelles. In mammals, lactate and malate dehydrogenase are the best-characterized enzymes whose targeting is controlled by functional translational readthrough.
Keywords: Dual targeting; Functional translational readthrough; Lactate dehydrogenase; Malate dehydrogenase; Peroxisome; Redox shuttle.