Structural and functional analysis of human liver-expressed antimicrobial peptide 2.
Human liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic antimicrobial peptide (CAMP) believed to have a protective role against bacterial infection. Little is known about the structure-activity relationships of LEAP-2 or its mechanism of action. In this study we describe the structure of LEAP-2, analyze its interaction with model membranes, and relate them to the antimicrobial activity of the peptide. The structure of LEAP-2, determined by NMR spectroscopy, reveals a compact central core with disorder at the N and C termini. The core comprises a β-hairpin and a 3(10)- helix that are braced by disulfide bonds between Cys17-28 and Cys23-33 and further stabilized by a network of hydrogen bonds. Membrane-affinity studies show that LEAP-2 membrane binding is governed by electrostatic attractions, which are sensitive to ionic strength. Truncation studies show that the C-terminal region of LEAP-2 is irrelevant for membrane binding, whereas the N-terminal (hydrophobic domain) and core regions (cationic domain) are essential. Bacterial-growth-inhibition assays reveal that the antimicrobial activity of LEAP-2 correlates with membrane affinity. Interestingly, the native and reduced forms of LEAP-2 have similar membrane affinity and antimicrobial activities; this suggests that disulfide bonds are not essential for the bactericidal activity. This study reveals that LEAP-2 has a novel fold for a CAMP and suggests that although LEAP-2 exhibits antimicrobial activity under low-salt conditions, there is likely to be another physiological role for the peptide.
Henriques
Sónia Troeira
ST
Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072 Australia.
Tan
Chia Chia
CC
Craik
David J
DJ
Clark
Richard J
RJ
D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000737:chemistry*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D001798:Blood Proteins / Q000737:chemistry*; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D008051:Lipid Bilayers; D010743:Phospholipids; C475606:liver-expressed antimicrobial peptide 2, human