Blocks Z-ring formation in the mother cell during sporulation by inhibiting the polymerization of FtsZ (PubMed:18284588, PubMed:23237472, PubMed:25848052). Binds to the minus end of FtsZ and functions as a filament-capping protein (PubMed:25848052). At high concentrations, is capable of both capping and sequestration of FtsZ (PubMed:25848052). Decreases the GTPase activity of FtsZ (PubMed:18284588, PubMed:23237472, PubMed:25848052). Highly effective in inhibiting polymerization at low and intermediate concentrations of GTP and only partially effective at high GTP concentrations. Interacts with FtsZ (PubMed:18284588, PubMed:23237472, PubMed:25848052). Binds to the C-terminal polymerization interface of FtsZ (PubMed:25848052). Binds to FtsZ filaments (PubMed:25848052). Expressed at an intermediate stage of sporulation. Expression is regulated by the mother cell-specific factor sigma E. Ray et al suggested that MciZ competes with GTP for binding to FtsZ, but Bisson-Filho et al showed later that MciZ and GTP bind at opposite surfaces of FtsZ, and that MciZ does not compete with GTP binding.