Subcloning the genes encoding the metallopeptidase and response
regulator
The full-length metallopeptidase gene alone (pCRC01), the full-length regulator gene alone
(pCRC03) and the combination of both the metallopeptidase and the regulator gene (pCRC02)
were subcloned in a pET28b (Novagen, Madison, WI) background using primers (Table 2) targeting
XbaI and BamHI restriction enzyme sites (pCRC01, pCRC02), or NcoI and BamHI restriction
enzyme sites (pCRC03) present in the pET28b multicloning region. A Thr to Ala
mutation was introduced at Thr2 in the regulator gene coding sequence in pCRC03 to facilitate
cloning using the NcoI restriction enzyme site.
To construct a system in which the genes present on these constructs would be expressed in
an E. coli strain in the absence of the λDE3 lysogen, a native E. coli promoter (uvrA) was cloned
into each of these constructs using preexisting BglII and XbaI restriction enzyme sites from
their respective pET28b multicloning regions. The cloned promoter DNA was engineered with
these restriction enzyme sites, and was constructed from two synthetic oligonucleotides that
were annealed and digested accordingly (Table 2). This strategy directly added the native
E. coli promoter, displacing the existing T7 promoter region. The newly constructed vectors
were named pCRC01UVRA, pCRC02UVRA, and pCRC03UVRA, according to the notation
introduced in the above paragraph. Verification of expression was performed by SDS-PAGE
analysis of the protein from EPI300 E. coli containing pCRC03UVRA as well as
phenotypic assays.