Topological Stability and Self-Association of a Completely Hydrophobic Model Transmembrane Helix in Lipid Bilayers

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• 作者：Yoshiaki Yano ; Tomokazu Takemoto ; Satoe Kobayashi ; Hiroyuki Yasui ; Hiromu Sakurai ; Wakana Ohashi ; Miki Niwa ; Shiroh Futaki ; Yukio Sugiura ; and Katsumi Matsuzaki
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：March 5, 2002
• 年：2002
• 卷：41
• 期：9
• 页码：3073 - 3080
• 全文大小：84K
• 年卷期：v.41,no.9(March 5, 2002)
• ISSN：1520-4995

文摘

Investigation of interactions between hydrophobic model peptides and lipid bilayers is perhapsthe only way to elucidate the principles of the folding and stability of membrane proteins (White, S. H.,and Wimley, W. C. (1998) Biochim. Biophys. Acta 1367, 339-352). We designed the completelyhydrophobic "inert" peptide modeling a transmembrane (TM) helix without any of the specific side-chaininteractions expected, X-(LALAAAA)₃-NH₂ [X = Ac (I), 7-nitro-2-1,3-benzoxadiazol-4-yl (II), or 5(6)-carboxytetramethylrhodamine (III)]. Fourier transform infrared-polarized attenuated total reflectionmeasurements revealed that I as well as II assume a TM helix in hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers. Dithionite quenching experiments detected no topological change (flip-flop) in the helix II for at least 24 h. Thus, the TM helix itself is a highly stable structure, even in theabsence of flanking hydrophilic or aromatic amino acids which are suggested to play important roles instable TM positioning. Helix self-association in lipid bilayers was detected by fluorescence resonanceenergy transfer between II and III. The peptide was in a monomer-antiparallel dimer equilibrium withan association free energy of ~-13 kJ/mol. Electron spin resonance spectra of 1-palmitoyl-2-stearoyl-(14-doxyl)-sn-glycero-3-phosphocholine demonstrated the presence of a motionally restricted componentat lower temperatures.