Activation　of　pro-sigma(K)　processing　requires　a　signaling　protease　SpoIVB　that　is　secreted　from　the　forespore　into　the　space　between　the　two　cells　during　sporulation　in　Bacillus　subtilis.　Bypass　of　forespore　protein　C　(BofC)　is　an　inhibitor　preventing　the　autoproteolysis　of　SpoIVB,　ensuring　the　factor　sigma(K)　operates　regularly　at　the　correct　time　during　the　sporulation.　However,　the　regulatory　mechanisms　of　BofC　on　pro-sigma(K)　processing　are　still　unclear,　especially　in　the　aspect　of　the　interaction　between　BofC　and　SpoIVB.　Herein,　the　recombinant　BofC　(rBofC)　was　expressed　in　the　periplasm　by　the　E.　coli　expression　system,　and　crystal　growth　conditions　were　obtained　and　optimized.　Further,　the　crystal　structure　of　rBofC　was　determined　by　X-ray　crystallography,　which　is　nearly　identical　to　the　structures　determined　by　NMR　and　predicted　by　AlphaFold.　In　addition,　the　modeled　structure　of　the　BofC-SpoIVB　complex　provides　insights　into　the　molecular　mechanism　by　which　domain　1　of　BofC　occupies　the　active　site　of　the　SpoIVB　serine　protease　domain,　leading　to　the　inhibition　of　the　catalytical　activity　of　SpoIVB　and　prevention　of　the　substrate　of　SpoIVB　(SpoIVFA)　from　binding　to　the　active　site.