The membrane remodeling protein Pex11p activates the GTPase Dnm1p during peroxisomal fission.

The initial phase of peroxisomal fission requires the peroxisomal membrane protein Peroxin 11 (Pex11p), which remodels the membrane, resulting in organelle elongation. Here, we identify an additional function for Pex11p, demonstrating that Pex11p also plays a crucial role in the final step of peroxisomal fission: dynamin-like protein (DLP)-mediated membrane scission. First, we demonstrate that yeast Pex11p is necessary for the function of the GTPase Dynamin-related 1 (Dnm1p) in vivo.

Preperoxisomal vesicles can form in the absence of Pex3.

We demonstrate that the peroxin Pex3 is not required for the formation of peroxisomal membrane structures in yeast pex3 mutant cells. Notably, pex3 mutant cells already contain reticular and vesicular structures that harbor key proteins of the peroxisomal receptor docking complex-Pex13 and Pex14-as well as the matrix proteins Pex8 and alcohol oxidase. Other peroxisomal membrane proteins in these cells are unstable and transiently localized to the cytosol (Pex10, Pmp47) or endoplasmic reticulum (Pex11).

Isolation of mutants of Hansenula polymorpha defective in the assembly of octameric alcohol oxidase.

Alcohol oxidase (AO) is a peroxisomal enzyme that catalyses the first step in methanol metabolism in yeast. Monomeric, inactive AO protein is synthesised in the cytosol and subsequently imported into peroxisomes, where the enzymatically active, homo-octameric form is found. The mechanisms involved in AO octamer assembly are largely unclear.

Normal peroxisome development from vesicles induced by truncated Hansenula polymorpha Pex3p.

We show that the synthesis of the N-terminal 50 amino acids of Pex3p (Pex3p(1-50)) in Hansenula polymorpha pex3 cells is associated with the formation of vesicular membrane structures. Biochemical and ultrastructural findings suggest that the nuclear membrane is the donor membrane compartment of these vesicles. These structures also contain Pex14p and can develop into functional peroxisomes after subsequent reintroduction of the full-length Pex3p protein.