The evolution of oligomerization factors of membrane-spanning alpha-helical segments into lipid bilayers

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In order to search the oligornerization mechanism of membrane-spanning alpha-helical segments of membrane protcins into biomembranes, we designed and synthesized the following peptides :Ac-Lys2-Gly-Leu24-Lys2-Ala-NH2・・・・・・・・・・・・・・P24Ac-Lys12-Gly-Leu9TrpLeu2-Glu-Leu11-Lys2-Ala-NH12・・・P24EWAc-Lys12-Gly-Leu9-Xxx -Leu2-Lys-Leu11-Lys2-Ala-NH2・・・P24KPyaAc-Lys12-Gly-Leu9TrpLeu14-Lys2-Ala-NH2・・・・・・・P24-WAc-Lys12-Gly-Leu9-Xxx-Leu14-Lys2-Ala-NH2・・・・・・・P24-PyaThe11w peptide P24, which has been well characterized as a membrane spanning a-helical peptide, was used as a host peptide. The P24-W and P24-Pya were introduced Trp and Pya (alpha-pyreny1alanine) residues at an appropriate positions of P24, respectively, to investigate whether the peptide itself oligonmize or not in lipid bilayer. If the both peptides oligomize into lipid bilayer, an energy transfer between indole and pyrene chromphores should be observed. P24EW and P24KPya were introduced Gln and Lys residues, respectively, into the corresponding fluorescence peptides, to investigate the effect of charge interaction on oligomerization. The strong energy transfer was observed between P24W and P24Pya when they were incorporated into lipid bilayers, but no different energy transfet effect was observed between two P24W - P24Pya and P24EW-P24KPya into lipid bilayers. These results indicate that membrane-spanning alpha-helical peptides can aggregate themselves (oligomize) into lipid bilayers between alpha-helical segments of membrane proteins irrespective to the charge interaction.