Practice question

Peroxisomes are single membrane organelles handling beta oxidation of very long chain fatty acids, alpha oxidation, plasmalogen synthesis and H2O2 detoxification via catalase. Their abundance adapts to metabolic demand through fission of preexisting organelles rather than solely de novo budding from ER. Pex11 family proteins, including Pex11 alpha beta gamma isoforms in mammals, are conserved peroxisomal membrane proteins enriched in regions of high curvature. Upon induction by oleate, fibrates via PPAR alpha, or cold, PEX11 genes transcribed, proteins oligomerize through amphipathic helices and induce membrane elongation forming tubular juxtaposed elongated peroxisomes JEPs. These elongated intermediates acquire fission adaptors Fis1, Mff and tail anchored GDAP1 recruiting dynamin related GTPases Drp1 DLP1 that assemble helical collars constricting membrane in GTP dependent manner for scission. Yeast pex11 deletion yields few enlarged peroxisomes, overexpression produces many small ones. Pex11 does not transport iron, does not act as importomer for matrix proteins which requires Pex5 Pex14, and is unrelated to lysosomal degradation, its dedicated role is membrane remodeling for proliferation.