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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.