Recombinant plectasin, the first fungus defensin, was expressed in Pichia pastoris and purified, and its physical, chemical and antimicrobial characteristics were studied. Following a 120 h induction of recombinant yeast, the amount of total secreted protein reached 748.63 μg/ml. The percentage of recombinant plectasin was estimated to be 71.79% of the total protein. After purification with a Sephadex G-25 column and RP-HPLC, the identity of plectasin was verified by MALDI-TOF MS. Plectasin exhibited strong antimicrobial activity against the Gram-positive bacteria Staphyloccocus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Streptococcus suis. At a concentration of 2560 μg/ml, this peptide showed approximately equal activity against S. aureus, S. epidermidis, S. suis, and S. pneumoniae, when compared to 320 μg/ml vancomycin, 640 μg/ml penicillin, 320 μg/ml vancomycin and 160 μg/ml vancomycin, respectively. In addition, plectasin showed anti-S. aureus activity over a wide pH range of 2.0 and 10.0, a high thermal stability at 100 °C for 1 h and remarkable resistance to papain and pepsin. The expression and characterization of recombinant plectasin in P. pastoris has potential to treat Streptococcus and Staphyloccocus infections when most traditional antibiotics show no effect on them. Our results indicate that plectasin can be produced in large quantities, and that it has pharmaceutical importance for the prevention and clinical treatment of Staphyloccocus and Streptococcus infections. © 2011 Elsevier Inc. All rights reserved.
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