Objective: To construct pcDNA4/His C-MBL recombinant eukaryotic expression plasmid and examine its expression of mannan-binding lectin (MBL) in mammary cells.
Methods: The target sequence was amplified by PCR from pGEM-MBL plasmid that contains wild-type human MBL cDNA, and inserted into eukaryotic expression vector PcDNA4/His C followed by restriction mapping and sequencing. The recombinant plasmid PcDNA4/His C-MBL was transformed into Chinese-hamster ovary (CHO) cells by electroporation, and the Zeocin-resistant clones were selected for analysis of mRNA expression by reverse transcription (RT)-PCR. The expressed product was purified by immobilized metal affinity chromatography (IMAC) and identified by SDS-PAGE and Western-blot analysis, and its immunoreactivity was detected by an indirect enzyme-linked immunosorbent assay ELISA using the anti-serum from Balb/C mice immunized with the recombinant protein.
Results: The cDNA fragment of 750 bp was amplified from pGEM-MBL plasmid, which was shown by restriction enzyme digestion and DNA sequencing. The mRNA expression of Zeocin-resistant CHO cell clones was detected by RT-PCR. Three components of 29, 58 and 87 kD in the purified recombinant product were found by SDS-PAGE and the 29 kD component could be recognized by anti-6His antibody in Western blot analysis. The titers of the anti-serum from immunized mice were 1: 819 200 against the recombinant protein and 1:25 600 against both the natural human MBL and the recombinant trimeric carbohydrate-recognition domain (CRD) of human MBL, as determined by the indirect ELISA.
Conclusion: The cell strains that express recombinant human MBL (rhMBL) and rhMBL protein have been obtained successfully, which provides the basis for further research of MBL molecule.