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KMID : 0366319920120020091
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Biochemistry and Molecular Biology News
1992 Volume.12 No. 2 p.91 ~ p.97
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Abstract
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It has been well established that a-helix is a predominant structural motif for the membrane-spanning segments of integral proteins. This is because, by forming intra-chain hydrogen bonds, the highly polar peptide bonds can hide from the hydrophobic acyl chains of the lipids in the membrane interior. The a-helical structure is also very common for the proteins which are bound on the membrane surface despite of the fact that segregation of peptide bond from the hydrophobic phase is not a prevailing concern. Similar situation also occurs when proteins form interface between exposed acyl chains of lipid bilayer and aqueous phase in the micellar complex. The a-helical structures in these interface proteins are generally amphiphilic because they are in contact with both hydrophobic and hydrophilic phases. It was proposed that a preformed amphiphilic a-helix is not nt,cessary for the micellization. The hydrophobic residues of a potentially amphiphilic a-helix may be able to interact with phospholipid. In this lipid-protein interaction an amphiphilic a-helix is formed and hydrophobic residues are buried in phospholipid bilayer. Finally, the exposed hydrophobic edges of micellar complex are shieled from the aqueous phase by amphiphilic helices. This micellization induced by protein wasused as a model system to study the role of amphiphilic helices in lipid-protein associations.
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