Molecular organization of the antimicrobial peptide jelleine in model membranes
The antimicrobial peptide jelleine-I (PFKLSLHL) was previously shown to inhibit growth of Staphylococcus epidermidis and Eschericia coli. But a detailed description of the microbial killing mechanism is still lacking. Most of the studies have focused on the interactions between jelleine and negatively changed lipid head groups as found in bacterial membranes. This study is assessing the interactions involving zwitterionic phosphocholine lipids, which are the main component in the outer leaflets of eukaryotic cells. For this, we investigated the effect of lipid binding on the secondary structure and thermal stability of the antibacterial peptide jelleine using infrared, fluorescence, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The selected model membranes are the lipids DPPC, DOPC, POPC, and cholesterol, the binary lipid mixtures of DPPC-DOPC, DPPC-CHOL, DOPC-CHOL, and the ternary lipid mixtures of DPPC-DOPC-CHOL, DPPC_POPC-CHOL (lipid rafts). FTIR, TGA and DSC revealed that the association jelleine-DPPC, under our experimental conditions, is the most stable. FTIR with its curve fitting procedures were applied for quantitative analysis of peptide conformation variations. The quantitative analysis of peptide secondary structure of the free jelleine showed a major β-sheet structure (55%) with turns structure (45%) as minor component of the peptide conformation. Jelleine interacts with DPPC through a conformation change, and through the C=O and phosphate groups. With DOPC and POPC, jellein interacts through the ammonium group and conformational change. Jelleine interacts with cholesterol through a conformation change only. Fluorescence data show a stronger interaction of jellein with DPPC and a weak interaction of jelleine with cholesterol. Cholesterol reduced the power of jelleine to bind to model membranes. In the 25-400°C temperature range, jelleine-DPPC is more stable than jelleine itself. The presence of cholesterol destabilizes the mixture jelleine-DPPC. DSC data indicated that jelleine is a very stable compounds but the jelleine-DPPC complex seems to be the most stable among the mixtures. Cholesterol reduced the interaction between jelleine and other model membranes. Our results provide new insights into the structure of jelleine in the presence of model membranes that can be taken into account for future studies on the mechanism of interaction between jelleine and model membranes.
Nujud Aqeel Andijani,
"Molecular organization of the antimicrobial peptide jelleine in model membranes"
ETD Collection for Tennessee State University.