The non-disulphidebridged AMP Vejovine from the scorpion Vaejovis mexicanus can inhibit the growth of multidrug resistant clinical isolates of gramnegative bacteria. These findings make scorpion venom as a ML 10302 potential source for discovering AMPs. We focus our interest on the scorpion species Heterometrus petersii, which usually inhabits in tropical to subtropical rainforests. Various kinds of bacteria can grow and proliferate in this kind of living environment, which is conducive to the evolution of the scorpion venom to contain more AMPs. In this study, a new AMP named Hp1404 was characterized from the venomous gland cDNA library of the scorpion Heterometrus petersii. Hp1404 is an amphipathic a-helical peptide. The in vitro antibacterial activities of Hp1404 peptide were then investigated using both standard and resistant strains. The mechanism of Hp1404 against bacteria was further explored in our work. Finally, we tested the toxicities of Hp1404 against mammalian cells and mice and the protective effect of Hp1404 against infection to evaluate its potential application as an antibacterial agent. Previous studies showed that the interaction (+)-Methamphetamine hydrochloride between AMPs and LPS or LTA is important to the activity of AMPs. Our results showed that the antibacterial activity of Hp1404 was not interfered with LTA or LPS, which was different from the peptide Kn2�C7, a scorpion AMP derivative studied in our previous work. It implied that LPS or LTA might not be the primary antimicrobial action site of Hp1404. Our further data by biolayer interferometry experiments showed that Hp1404 did not interact with LPS or LTA indeed. Thus, the mode of action of Hp1404 may be different from that of most classical AMPs. Though Hp1404 do not interact with LTA, two factors may let it successful reach the action sites and perform its activity against gram-positive bacteria: The structure of the gram-positive bacteria cell wall. Such as S. aureus cell, which has a loosely arrayed network on the cell surface, consisting of fibrils and pores ranging in size from 50 to 500 A ��, while the Hp1404 molecule is about 20�C50 A ��. These pores are large enough to let the peptide molecules to pass through them. Hp1404 is a cationic peptide, while there are a lot of negatively charged molecules outside the bacterial cell, the electrostatic bonding between Hp1404 and bacteria will encourage the cationic peptide to pass through the cell wall.