NUCLEOTIDE SEQUENCE OF THE STAPHYLOCOAGULASE GENE FROM STAPHYLOCOCCUS AUREUS STRAIN BB
Staphylocoagulase (SC) is a secretary protein produced by several strains of Staphylococcus aureus (S. aureus). This protein forms a molecular complex ("staphylothrombin") with human prothrombin in a molar ratio of 1:1. The complex displays the ability to clot fibrinogen and to hydrolyze the synthetic tripeptide substrates for α-thrombin. The formation of staphylothrombin does not require proteolytic cleavage of the prothrombin molecule, and this mechanism differs markedly from the activation process by either blood-clotting factor Xa or snake venom procoagulant.In the present studies, a pAT153 library containing partial Mbo I-digested DNA prepared from aureus strain BB has been screened with a fibrin gel formation method. The identity of these clones with SC was confirmed by DNA sequence analysis and by comparison of the derived amino acid sequence with that determined for the purified SC protein. One of the positive colonies was isolated and 3.1 Kb of the insert DNA was determined by the dideoxy chain termination method. The results indicated that the insert DNA consists of 148 bp 5' flanking region, protein coding region of 715 amino acids and 746 bp 3' flanking region, and that SC from strain BB is synthesized as a precursor with a signal peptide of 26 amino acids. Thus, the mature form was composed of 689 amino acids with a molecular weight of 77,337- The NH2-terminal sequence (324 amino acids) of SC isolated from S. aureus strain 213 (S. Kawabata et al. (1986): J. Biol. Chem. 261, 527-531) was compared with that of SC derived from strain BB. The sequence homology between them was found to show 57 %. It was also found that SC derived from strain BB was composed of 8 tandem repeats (27 amino acid residues in length) in the COOH-terminal region, although their functions are not known.