Part:BBa_K2020003

mutated expression system for subtilisin E in E. coli (S221Y)

Once introduced into E. coli, this BioBrick is able to produce an inactive version of subtilisin E and simultaneously secret the enzyme into the periplasm of the cell. By performing a site-directed mutagenesis, serine in the catalytic triad of the enzyme was exchanged against tyrosine. As a consequence, the enzyme looses its proteolytic activity.

For the varification of the function of this part, a skim milk assay on agar plates containing IPTG and the needed antibiotics was performed. Therefore, we streaked out the cells containing the modified expression systems on these plates and incubated at 30°C for three days.

The figure shows the skim milk plates assay. Cells containing the empty backbone (1) in comparison to either cells producing the native protease (2), cells with the SDM 1-modified (3) and the SDM 3-modified expression system (4) after incubation for 3 days at 30°C.

Neither the empty backbone nor the SDM 1 modified expression system did seem to cause a proteolytic activity. A clearance and therefore a proteolytic activity could only be observed for the native protease (as demonstrated for the BioBrick K2020002. By demonstrating that this modification doesn’t result in a clearance of the skim milk plates, we were now able to prove that serine is essential for the proteolytic activity of the protease and that exchanging it would inactivate the enzyme. Hence, we demonstrated that exchanging serine against a photo-labile, non-canonical amino acid will inactivate subtilisin E and therefore proved the principle of our project.

Usage and Biology

Subtilisin E is an alkaline serine protease which non-specifically digests proteins. It is naturally produced by Bacillus subtilis.

This composite part consists of the promoter BBa_R0010, the ribosome binding site BBa_B0034, the newly created BioBrick part BBa_K2020001 and the terminator BBa_B0010. BioBrick BBa_K2020001 is a composite part itself and includes the secretion tag pelB (BBa_J32015) and a subtilisin E gene optimized for E. coli codon usage (BBa_K2020000).

This mutated version of the BioBrick BBa_K2020002 was created to prove that serine²²¹ in the catalytic triad of subtilisin E is essential for the activity of the enzyme.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 280
  
• 1000
  COMPATIBLE WITH RFC[1000]