Antimicrobial defensins with the cysteine-stabilized alpha-helical and beta-sheet (CS alpha beta) motif are widely distributed in three eukaryotic kingdoms. However, recent work suggests that bacteria Could possess defensin-like peptides (DLPs). Here, we report recombinant expression, in vitro folding, structural and functional characterization of a DLP from the myxobacterium Anaeromyxobacter dehalogenans (AdDLP). Circular dichroism analysis indicates that recombinant AdDLP adopts a typical structural feature of eukaryotic defensins, which is also consistent with an ab initio structure model predicted using I-TASSER algorithm. We found that AdDLP is an antimalarial peptide that led to more than 50% growth inhibition on sexual stages of Plasmodium berghei at micromolar concentrations and killed 100% intraerythrocytic Plasmodium falciparum at 10 mu M in a time-dependent manner. These results provide functional evidence for myxobacterial origin of eukaryotic defensins. High-level production of the pure anti-Plasmodium peptide Without harming mammalian red blood cells in Escherichia coli makes AdDLP an interesting candidate for antimalarial drug design. (C) 2009 Elsevier Inc. All rights reserved.