GENE FROM TROPICAL BACILLUS-SPHAERICUS ENCODING A PROTEASE CLOSELY-RELATED TO SUBTILISINS FROM ANTARCTIC BACILLI

We undertook to identify the protease(s) involved in the in vivo degra dation of the 100 kDa mosquitocidal toxin (Mtx) from Bacillus sphaeric us SSII-1 and isolated a B. sphaericus SSII-1 gene flanked upstream by a typical Shine-Dalgarno ribosome binding site and downstream by a st rong rho-independent transcription terminator, The predicted ORF encod es a 432 amino acid protein with significant homology throughout its s equence to two subtilisin-like serine proteases from the Antarctic psy chrophilic (cold-adapted) bacilli, TA39 and TA41. The predicted N-term inal sequence suggests that the B. sphaericus protease is related Co s fericase, a partially characterized serine protease from B. sphaericus . Only B. sphaericus strains which produce Mtx-degrading protease acti vity harbour the subtilisin-like protease gene, suggesting that this p rotease may be responsible for or contribute to the degradation of Mtx in B. sphaericus SSII-1. A 36-kDa protease with Mtx-degrading activit y and similar properties to sfericase was also purified from sporulate d cultures of B. sphaericus SSII-1. Further studies are needed to dete rmine tile relationship of this protease to sfericase and to the predi cted product of the subtilisin-like serine protease gene. (C) 1997 Els evier Science B.V.