PEROXISOME BIOGENESIS

Peroxisomes are eukaryotic organelles that are the subcellular locatio n of important metabolic reactions. In humans, defects in the organell e's function are often lethal, Yet, relative to other organelles, litt le is known about how cells maintain and propagate peroxisomes or how they direct specific sets of newly synthesized proteins to these organ elles (peroxisome biogenesis/assembly). In recent years, substantial p rogress has been made in elucidating aspects of peroxisome biogenesis and in identifying PEX genes whose products, peroxins, are essential f or one or more of these processes. The most progress has been made in understanding the mechanism by which peroxisome matrix proteins are im ported into the organelles. Signal sequences responsible for targeting proteins to the organelle have been defined. Potential signal recepto r proteins, a receptor docking protein and other components of the imp ort machinery have been identified, along with insights into how they operate. These studies indicate that multiple peroxisomal protein-impo rt mechanisms exist and that these mechanisms are novel, not simply va riations of those described for other organelles.