The cell envelope-bound metalloprotease (camelysin) from Bacillus cereus is a possible pathogenic factor

A novel membrane proteinase of the nosocomial important bacteria species Ba cillus cereus (synonyms: camelysin, CCMP) was purified up to homogeneity as was shown by mass spectrometry in its amphiphilic form. Camelysin is a neu tral metalloprotease with a molecular mass of 19 kDa. Its unique N-terminus Phe-Phe-Ser-Asp-Lys-Glu-Val-Ser-Asn-Asn-Thr-Phe-Ala-Ala-Gly-Thr-Leu-Asp-Le u-Thr-Leu-Asn-Pro-Lys-Thr-Leu-Val-Asp-(Ile-Lys-Asp)- was not detected in th e protein data bases during BLAST searches, but in the partially sequenced genome of Bacillus anthracis, coding for an unknown protein. Cleavage sites of the membrane proteinase for the insulin A- and B-chains were determined by mass spectrometry and N-terminal sequencing. Camelysin prefers cleavage sites in front of aliphatic and hydrophilic amino acid residues (-OH, -SO3 H, amido group), avoiding bulky aromatic residues. The internally quenched fluorogenic substrates of the matrix metalloproteases 2 and 7 were cleaved with the highest efficiency at the Leu- down arrow -Gly or Leu- down arrow -Ala bond with the smaller residue in the P-1' position. The protein specif icity is broad - all various kinds of casein were cleaved as well as acid-s oluble collagen, globin and ovalbumin; intact insulin was destroyed only to a low extent. Actin, collagen type I, fibrinogen, fibrin, alpha (2)-antipl asmin and alpha (1)-antitrypsin were cleaved. The protease formed SDS-stabl e complexes with Glu-plasminogen and antithrombin III, visible after SDS el ectrophoresis by gold staining and Western blot. The CCMP-plasminogen compl ex caused a partial activation of plasminogen to plasmin. Camelysin interac ts with proteins of the blood coagulation cascade and could facilitate the penetration of fibrin clots and of the extracellular matrix during bacteria l invasion. (C) 2001 Elsevier Science B.V. All rights reserved.