This family includes both microviridins and marinostatins. It seems likely that in both cases it is the C-terminus which becomes the active inhibitor after post-translational modifications of the full length, pre-peptide. it is the ester linkages within the key, 12-residue. region that circularize the molecule giving it its inhibitory conformation.
Lu S et al.(2020). "CDD/SPARCLE: the conserved domain database in 2020.",