Purity > 90% as determined by SDS-PAGE. MW: 41.7kDa. Full Length of Mature Protein: 19-378aa. N-terminal 6xHis-tagged. Rattus norvegicus (Rat). Protease inhibitor required for egg fertilization. Required to prevent premature zona pellucida hardening before fertilization, probably by inhibiting the protease activity of ASTL, a protease that mediates the cleavage of ZP2 and triggers zona pellucida hardening