NMR studies of aurein 1.2 analogs.
Aurein 1.2 is an antimicrobial and anticancer peptide isolated from an Australian frog. To improve our understanding of the mechanism of action, two series of peptides were designed. The first series includes the N-terminal membrane anchor of bacterial glucose-specific enzyme IIA, aurein 1.2, and a newly identified aurein 1.2 analog from human LL-37 (LLAA). The order of antibacterial activity is LLAA>aurein 1.2>>the membrane anchor (inactive). The structure of LLAA in detergent micelles was determined by (1)H NMR spectroscopy, including structural refinement by natural abundance (13)C(alpha), (13)C(beta), and (15)N chemical shifts. The hydrophobic surface area of the 3D structure is related to the retention time of the peptide on a reverse-phase HPLC column. The higher activity of LLAA compared to aurein 1.2 was attributed to additional cationic residues that enhance the membrane perturbation potential. The second peptide series was created by changing the C-terminal phenylalanine (F13) of aurein 1.2 to either phenylglycine or tryptophan. A closer or further location of the aromatic rings to the peptide backbone in the mutants relative to F13 is proposed to cause a drop in activity. Phenylglycine with unique chemical shifts may be a useful NMR probe for structure-activity relationship studies of antimicrobial peptides. To facilitate potential future use for NMR studies, random-coil chemical shifts for phenylglycine (X) were measured using the synthetic peptide GGXGG. Aromatic rings of phenylalanines in all the peptides penetrated 2-5 A below the lipid head group and are essential for membrane targeting as illustrated by intermolecular peptide-lipid NOE patterns.
Li
Xia
X
Structure-Fun Laboratory, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
Li
Yifeng
Y
Peterkofsky
Alan
A
Wang
Guangshun
G
D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; C506635:aurein 1.2 peptide