Interaction hierarchy among Cdv proteins drives recruitment to membrane necks

Cell division in the crenarchaea is accomplished by the Cdv system. In Sulfolobus cells, it was observed that an initial non-contractile ring of CdvA and CdvB forms at the mid location of the cell, which is followed by a second ring of CdvB1 and CdvB2 that appear to drive the constriction of the cell membrane. Here, we use an in vitro reconstituted system to explore how protein interactions among these Cdv proteins govern their recruitment to the membrane. We show that CdvA does not bind the membrane unless in complex with CdvB. We find that CdvB2 can polymerize if its self-inhibitory domain is removed, and that by itself is exhibits poor binding to the membrane. However, CdvB2 can be efficiently recruited to the membrane by both CdvB1 and CdvB. Furthermore, the CdvB1:CdvB2 co-polymer can be recruited to the membrane by CdvA:CdvB. By reconstituting these proteins in dumbbell-shaped liposomes, we show that Cdv proteins have a strong preference to localize at membrane necks of high curvature. Our findings clarify many of the mutual protein interactions of the Cdv system and their interaction with the membrane, thus helping to build a mechanistic understanding of cell division in archaeal cells.