Studies of the human defensins have been hampered by the lack of a simple expression system allowing for rapid production of functional peptide forms. Here, we describe a Saccharomyces cerevisiae AH22 expression system that meets that condition. The 42 amino acid form of human beta-defensin-1 was expressed under the control of the ADH1 promoter. The optimum conditions for expression were determined and the stable maintenance of the pVT103L-hBD-1 chimeric vector in the yeast population was confirmed. Expressed hBD-1 was secreted into the medium (approximately 55 microg l(-1)) and purified using cation-exchange chromatography. Isolated defensin exhibited strong bactericidal effect on Escherichia coli ML-35p. We conclude that the expression system described here will be a useful tool where readily prepared and active forms of the human defensins are needed.

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