Cloning, sequencing, and expression of a minor protease-encoding gene from Serratia marcescens ATCC21074

The gene (smp) encoding an extracellular protease (Smp) from Serratia marcescens ATCC21074 has been cloned and expressed in Escherichia coli HB101. The nucleotide (nt) sequence of the cloned smp gene revealed a single open reading frame of 1056 bp coding for 352 amino acids (aa) (38,479 Da). The N-terminal aa sequence of Smp excreted from the E. coli host cells revealed that mature Smp consists of 300 aa (32,515 Da). The deduced aa sequence of Smp showed high overall homology (43%) to the Erwinia carotovora metalloprotease, but low homology (15-20%) to other metalloproteases, including the S. marcescens major metalloprotease. The location for three zinc ligands and the active site for Smp was predicted from other metalloproteases. The biochemical properties of Smp show that this enzyme is a metalloprotease whose activity is optimal at pH 8.0 and 50 degrees C.