Cloning, expression and purification of penicillin-binding protein 3 from Pseudomonas aeruginosa CMCC 10104

• A truncated version of ftsI gene was amplified.
• The cloned DNA shared 99.76% identity with ftsI from PAO1.
• The recombinant PBP3 (rPBP3) was mainly expressed in soluble form.
• Penicillin-binding activity was tested to ensure the rPBP3 remained active.
• The protocol offers a method for obtaining high level of purified rPBP3.

Penicillin-binding protein 3 (PBP3) of Pseudomonas aeruginosa is the primary target of β-lactams used to treat pseudomonas infections. Meanwhile, structure change and overproduction of PBP3 play important roles in the drug resistance of P. aeruginosa. Therefore, studies on the gene and structure of PBP3 are urgently needed. P. aeruginosa CMCC 10104 is a type culture strain common used in China. However, there is no report on its genomic and proteomic profiles. In this study, based on ftsI of P. aeruginosa PAO1, the gene encoding PBP3 was cloned from CMCC 10104. A truncated version of the ftsI gene, omitting the bases encoding the hydrophobic leader peptide (amino acids 1–34), was amplified by PCR. The cloned DNA shared 99.76% identity with ftsI from PAO1. Only four bases were different (66 C-A, 1020 T-C, 1233 T-C, and 1527 T-C). However, there were no differences between their deduced amino acid sequences. The recombinant PBP3 (rPBP3), containing a 6-histidine tag, was expressed in Escherichia coli BL21 (DE3). Immobilized metal affinity chromatography (IMAC) with Ni2+–NTA agarose was used for its purification. The purified rPBP3 was identified by SDS–PAGE and western blot analysis, and showed a single band at about 60 kDa with purity higher than 95%. The penicillin-binding assay indicated that the obtained rPBP3 was functional and not hindered by the presence of the C-terminal His-tag. The protocol described in this study offers a method for obtaining purified recombinant PBP3 from P. aeruginosa CMCC 10104.