RESUMO
Objective To reconstruct the proteinic sequence of human cathelicidin LL-37 to increase the bactericidal activity of LL-37 and to express the reconstructed LL-37 (rLL-37) in bacterium. Methods The two dimensional structure, three dimensional structure and chemical characteristic of LL-37 were analyzed by Soft Ware Anthepro 5.0 and SWISS-MODEL. Without the three dimensional changes of LL-37, some negative amino acids of human cathelicidin LL-37 were replaced by positive amino acids and the positive charge of LL-37 was increased. According to the proteinic sequence changes of rLL-37, the DNA sequence of rLL-37 was reconstructed by Touch-Down PCR and recombined with vector pET-28a (+), thus rLL-37 was expressed in E.coli. BL21 (DE3) by the induction of IPTG and was purified by chromatography. Results Glu~ 16 , Asp~ 26 , Glu~ 36 of LL-37 were replaced by Gln~ 16 , Asn~ 26 , Gln~ 36 and the static charge of LL-37 was increased from +5.8 to +9.0 at pH 7.4. The DNA sequence of rLL-37 was reconstructed and inserted into vector pET-28a (+), the rLL-37 was expressed in E.coli. BL21 (DE3) and purified by strong cation exchange supports Macro-Prep High S successfully. The rLL-37 was proved by the means of inhibitory zone to be able to kill Gram-negative bacteria and Gram-positive bacteria. Conclusion It is feasible to reconstruct human cathelicidin LL-37 and express the protein in bacteria by fusion, which make it possible to produce more rLL-37 and study its biological function deeply.
RESUMO
Objective To employ 2 approaches to construct and express reconstructed LL-37 (rLL-37) in procaryotic system, and to explore a better preparation method. Methods The first method: the rLL-37 was inserted into vector pET-28a (+), then was induced to express in E.coli. BL21 (DE3) and purified by chromatography; the second method: the rare codons in the rLL-37 gene sequence were substituted by the preferred codons of procaryotic cell, and a fragment of carrier protein molecule (CPM) was added to the N termination of the objective sequence to construct expression plasmid pET-30a(+)-CPM-rLL-37, then the rLL-37 was expressed in E.coli. BL21 Star(DE3) and purified by chromatography. The productive rates of the 2 methods were compared and the antimicrobial effects of obtained rLL-37 was studied. Results The first method: the DNA sequence of rLL-37 was obtained successively by Touch-Down PCR. The expression plasmid pET-30a(+)-CPM-rLL-37 was expressed with fusion protein in E.coli BL21 (DE3). The expression rate accounted for 20% of total bacterio-protein, then the expressed product was purified by using high positive ion exchange column Macro-Prep High S; The second method: a fragment of carrier protein molecule was designed that contained 28 amino-acid residue and its pHi was 2.7, net charge was-6.0 at pH 7.4. After the expression plasmid pET-30a(+)-CPM-rLL-37 was constructed successively, it was expressed in E.coli BL21 Star (DE3). The expressed fusion protein accounted for 35% of total bacterio-protein, then the expressed product was purified by using affinity binding chromatography with TALON resins successfully. The obtained 2 kinds of rLL-37 were able to kill both Gram-negative and-positive bacteria by the means of inhibitory zone. Conclusion It’s feasible to prepare efficiently rLL-37 in procaryotic system, which founds the basis for the further research on bactericidal activity of rLL-37.