To determine the structural requirements of arenicin-1 in exerting antifungal activity, a truncated peptide with an N-terminal deletion and a peptide with an Ala substitution for an Arg in the beta-turn region were characterised by comparison to arenicin-1. The antifungal activities of the analogues were 25-50% lower than arenicin-1. Trp fluorescence and circular dichroism spectroscopy showed that Trp in the N-terminus contributed to peptide penetration and Arg in the beta-turn to conformational transition. These results suggest that Trp in the N-terminus and Arg in the beta-turn play a pivotal role in the membrane-directed antifungal activity of arenicin-1.