Defining dynamin-based ring organizing center on the peroxisome-dividing machinery isolated from Cyanidioschyzon merolae

Abstract

Organelle division is executed by contraction of a ring-shaped supramolecular dividing machinery. A core component of the machinery is the dynamin-based (DB) ring conserved in the division of mitochondrion, plastid and peroxisome. Here, using isolated peroxisome-dividing (POD) machinery from a unicellular red algae, Cyanidioschyzon merolae, we identified a DB ring organizing center (DOC) that acts as an initiation point for the DB ring formation. C. merolae contains a single peroxisome whose division can be highly synchronized by light/dark stimulation, thus intact POD machinery can be isolated in bulk. DB ring homeostasis is maintained by turn-over of GTP-bound form of Dnm1 between the cytosol and division machinery via DOC. A single DOC is formed on the POD machinery with a diameter of 500-700 nm and the DB ring is unidirectionally elongated from DOC in a manner dependent on GTP concentration. During the later step of membrane fission, the second DOC is formed and constructs the double DB ring to make the machinery thicker. These findings provide new insight to define fundamental mechanisms underlying the dynamin-based membrane fission in eukaryotic cells.