Role of the hinge region and the tryptophan residue in the synthetic antimicrobial peptides, cecropin A(1-8)-magainin 2(1-12) and its analogues, on their antibiotic activities and structures

Biochemistry. 2000 Oct 3;39(39):11855-64. doi: 10.1021/bi000453g.


A 20-residue hybrid peptide CA(1-8)-MA(1-12) (CA-MA), incorporating residues 1-8 of cecropin A (CA) and residues 1-12 of magainin 2 (MA), has potent antimicrobial activity without toxicity against human erythrocytes. To investigate the effects of the Gly-Ile-Gly hinge sequence of CA-MA on the antibacterial and antitumor activities, two analogues in which the Gly-Ile-Gly sequence of CA-MA is either deleted (P1) or substituted with Pro (P2) were synthesized. The role of the tryptophan residue at position 2 of CA-MA on its antibiotic activity was also investigated using two analogues, in which the Trp2 residue of CA-MA is replaced with either Ala (P3) or Leu (P4). The tertiary structures of CA-MA, P2, and P4 in DPC micelles, as determined by NMR spectroscopy, have a short amphiphilic helix in the N-terminus and about three turns of alpha-helix in the C-terminus, with the flexible hinge region between them. The P1 analogue has an alpha-helix from Leu4 to Ala14 without any hinge structure. P1 has significantly decreased lytic activities against bacterial and tumor cells and PC/PS vesicles (3:1, w/w), and reduced pore-forming activity on lipid bilayers, while P2 retained effective lytic activities and pore-forming activity. The N-terminal region of P3 has a flexible structure without any specific secondary structure. The P3 modification caused a drastic decrease in the antibiotic activities, whereas P4, with the hydrophobic Leu side chain at position 2, retained its activities. On the basis of the tertiary structures, antibiotic activities, vesicle-disrupting activities, and pore-forming activities, the structure-function relationships can be summarized as follows. The partial insertion of the Trp2 of CA-MA into the membrane, as well as the electrostatic interactions between the positively charged Lys residues at the N-terminus of the CA-MA and the anionic phospholipid headgroups, leads to the primary binding to the cell membrane. Then, the flexibility or bending potential induced by the Gly-Ile-Gly hinge sequence or the Pro residue in the central part of the peptides may allow the alpha-helix in the C-terminus to span the lipid bilayer. These structural features are crucial for the potent antibiotic activities of CA-MA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Anti-Bacterial Agents / chemical synthesis*
  • Anti-Bacterial Agents / pharmacology
  • Antimicrobial Cationic Peptides / chemical synthesis*
  • Antimicrobial Cationic Peptides / pharmacology
  • Antineoplastic Agents / chemical synthesis*
  • Antineoplastic Agents / pharmacology
  • Bacillus subtilis / drug effects
  • Bacillus subtilis / growth & development
  • Electric Conductivity
  • Escherichia coli / drug effects
  • Escherichia coli / growth & development
  • Humans
  • Ion Channels / chemistry
  • Jurkat Cells
  • K562 Cells
  • Lipid Bilayers / chemistry
  • Magainins
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Peptide Fragments / chemical synthesis*
  • Peptide Fragments / pharmacology
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Tryptophan / chemistry*
  • Xenopus Proteins*


  • Anti-Bacterial Agents
  • Antimicrobial Cationic Peptides
  • Antineoplastic Agents
  • Ion Channels
  • Lipid Bilayers
  • Magainins
  • Peptide Fragments
  • Xenopus Proteins
  • magainin 2 peptide, Xenopus
  • cecropin A
  • Tryptophan

Associated data

  • PDB/1F0D
  • PDB/1F0E
  • PDB/1F0F
  • PDB/1FOG
  • PDB/1FOH