Antimicrobial peptides from human skin are an important component of the innate immune response and play a key role as a first line of defense against infectious. One such peptide is the recently discovered dermcidin-1L. To better understand its mechanism and to further investigate its antimicrobial spectrum, recombinant dermcidin-1L was expressed in Escherichia coli as a fusion protein and purified by affinity chromatography. The fusion protein was cleaved by factor Xa protease to produce recombinant dermcidin-1L L. Antimicrobial and hemolytic assays demonstrated that dermcidin-1L displayed microbicidal activity against several opportunistic nosocomial pathogens, but no hemolytic activity against human erythrocytes even at concentrations up to 100 muM. Structural studies performed by circular dichroism spectroscopy indicated that the secondary structure of dermcidin-1L was very flexible, and both alpha-helix and beta-sheet structures might be required for the antimicrobial activity. Our results confirmed previous findings indicating that dermcidin-1L could have promising therapeutic potentials and shed new light on the structure-function relationship of dermcidin-1L. (C) 2005 Elsevier Inc. All rights reserved.