Protein Import into Peroxisomes: the principles and methods of studying

Peroxisomes are essential intracellular organelles that involve many metabolic processes, such as β‐oxidation of very long‐chain fatty acids and synthesis of plasmalogen and bile acids as well as generation and degradation of hydrogen peroxide. These peroxisomal functions are fulfilled by strictly and spatiotemporally regulated compartmentation of the proteins catalysing these reactions. Defects in peroxisomal protein import results in inherited peroxisome biogenesis disorders in humans. Peroxisomal matrix and membrane proteins are synthesised on free ribosomes but transported into peroxisomes by distinct pathways determined by specific targeting signals and their receptors. The mechanism by which this is achieved has been clarified by identification of many PEX genes and the products named peroxins, the essential factors for peroxisome biogenesis. This article introduces several basic methods to investigate protein import into peroxisomes.