While these models are attractive, confirmation will require further study and more information on the structure of the proteins, their mode of interaction and how the drugs alter these interactions. Peroxisomes are single-Lomitapide Mesylate membrane bound, multifunctional and highly Tulathromycin B dynamic organelles of most eukaryotic cells, which fulfil important metabolic functions in hydrogen peroxide and lipid metabolism. Their function has also been linked to developmental processes, stress response, age-related disorders, and antiviral innate immunity. Remarkably, the peroxisomal compartment shows high plasticity and responds to developmental, environmental, and metabolic stimuli with alterations in organelle number, morphology and protein content. Peroxisomes can multiply by growth and division of pre-existing organelles or, as particularly demonstrated in yeast, can form de novo from the endoplasmic reticulum. Whereas considerable progress has been made in the identification of key factors involved in these processes, the underlying mechanisms and the regulation of these processes are only poorly understood. The assembly of peroxisomes and protein import into the organelle requires the action of essential proteins, so called peroxins, which are encoded by PEX genes. Mutations in many PEX genes have been identified as the cause of severe and often lethal peroxisome biogenesis disorders. Peroxisome formation by growth and division involves the deformation and elongation of the peroxisomal membrane, its constriction and final scission. Similar 
to de novo biogenesis from the ER, growth and division of peroxisomes follows a multistep maturation pathway, which results in the formation of new daughter peroxisomes. In mammals, Pex11 proteins are so far the only proteins discovered capable of deforming and elongating the peroxisomal membrane. Hence, the mechanistic details of peroxisomal growth and division and the individual functions of the human Pex11 proteins have attracted great attention as they have been linked to new disorders affecting peroxisome morphology and dynamics. It has recently been reported that Pex11 proteins feature amphipathic helices that can insert into the peroxisomal membrane, thus influencing membrane bending. In line with this, Pex11 proteins are suggested to reorganize the peroxisomal membrane prior to fission,, and to mediate interactions with the peroxisomal fission machinery. The machinery for membrane scission includes the membrane adaptor proteins Fis1 and Mff, which are involved in the recruitment of the dynamin-like large GTPase DLP1/Drp1 to constriction sites on the peroxisomal membrane. DLP1 is supposed to assemble in spiral-like structures around constricted membranes to mediate membrane scission through GTP hydrolysis leading to the formation of new peroxisomes. Interestingly, mitochondria and peroxisomes, which are metabolically linked to each other, share these key components of their division machinery supporting a closer interorganellar relationship,,, whereas Pex11 proteins are exclusively peroxisomal. Pex11 proteins are conserved amongst species; however, many organisms contain various ����isoforms���� which are poorly characterized on a functional level, and may differ in their biochemical properties. Furthermore, their membrane topology is not entirely clear and may vary amongst different species. The mammalian genome encodes for three Pex11 proteins, Pex11pa, Pex11pb, and Pex11pc, which are thought to be integral membrane proteins with their N- and C-termini facing the cytosol.