Required for complete septum migration and engulfment of the forespore compartment during sporulation. Required for stabilizing and recruiting of SpoIIP to the septal membrane. Component of the MPD complex composed of SpoIIM, SpoIIP and SpoIID. Localizes to the sporulation septum and to the second division site within the mother cell. Before the start of engulfment localizes to the septal midpoint, then spreads throughout the septum prior to becoming enriched at the leading edge of the engulfing membrane, where it remains until the completion of membrane migration. Some remain partially trapped at the septum during engulfment and upon completion of engulfment become dispersed in the outer forespore membrane. Localization of the MPD complex to the septal membrane is dependent on SpoIIB. Expression starts 2 hours post-sporulation. Results in a block at stage II of sporulation. No fully engulfed forespores. SpoIIP mislocalization from the septal membrane.