BBA - Biomembranes, 1993, Vol.1151(1), pp.76-82
A synthetic model peptide, H-(Leu-Alα-Arg-Leu) 3 -(Leu-Arg-Alα-Leu) 3 -OH (4 6 ) can form ion channels in planar lipid bilayers by taking an amphipathic α-helix (Agawa, Y., Lee, S., Ono, S., Aoyagi H., Ohno, M., Taniguchi, T., Anzai, K. and Kirino, Y. (1991) J. Biol. Chem. 266, 20218–20222). For further study of ion channels formed by this type of peptides, we planned to synthesize [Trp 1 ]-4 6 (Ser) and [Trp 12 ]-4 6 (Ser) in which a hydrophilic amino acid, Ser, was introduced in several positions of 4 6 instead of hydrophobic ones. This modification was expected to decrease the ability of membrane perturbation and to simplify various current levels of the channel observed for 4 6 . Furthermore, additional Trp was introduced to the N-terminus or position 12 to monitor the lipid—peptide interaction. CD study showed that both peptides formed a random structure in buffer, but an α-helix in the presence of egg PC and a β-structure in egg PC/egg PG (3:1). Moreover, addition of NaCl to the acidic liposomes induced the conformational transition in the peptide from β-structure to α-helix. Salt-induced conformational transition in the presence of acidic liposomes was discussed in terms of membrane binding and ion-channel formation in planar lipid bilayer. Despite introduction of hydrophilic residues instead of hydrophobic residues in 4 6 , the peptide showed nearly the same dye-release ability from egg PC- egg PG liposomes as 4 6 . [Trp 12 ]-4 6 (Ser) was able to form cation-selective ion channels with two levels of conductance (mainly 250 and occasionally 125 pS) in asolectin planar lipid bilayer, suggesting that appropriate orientation of hydrophobic and hydrophilic residues in amphipathic peptide can simplify channel current levels.
Conformational Transition ; Alpha Helix ; Lipid-Peptide Interaction ; Beta Structure ; Ion Channel Forming Peptide ; Liposome ; Chemistry
View record in ScienceDirect (Access to full text may be restricted)
View full text in ScienceDirect