Helix-turn-helix peptides that form α-helical fibrils:: Turn sequences drive fibril structure

被引:53
作者
Lazar, KL
Miller-Auer, H
Getz, GS
Orgel, JPRO
Meredith, SC
机构
[1] Univ Chicago, Dept Pathol, Chicago, IL 60637 USA
[2] Univ Chicago, Dept Chem, Chicago, IL 60637 USA
[3] Univ Chicago, Dept Biochem & Mol Biol, Chicago, IL 60637 USA
[4] Rosalind Franklin Univ Med & Sci, Dept Biochem, N Chicago, IL 60064 USA
[5] IIT, Dept Biol Chem & Phys Sci, Ctr Synchrotron Radiat Res & Instrumentat, Chicago, IL 60616 USA
关键词
D O I
10.1021/bi0509705
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Models of apolipoprotein A-I (apo A-I), the main protein of high-density lipoprotein, predict that it contains 10 amphiphilic, alpha-helical segments connected by turns. We synthesized four peptides with two identical 18-residue, amphiphilic, alpha-helical segments (Anantharamaiah, G. M., et al. (1985) J. Biol. Chem. 260, 10248-10255) connected by putative turn sequences from apo A-I: (1) AcDWLKAFYDKVAEKLKEAFKVEPLRADWLKAFYDKVAEKLKEAF-NH2, (2) Ac-DWLKAFYDKVAEKLKEAFGLLPVLEDWLKAFYDKVAEKLKEAF-NH2, (3) Ac-DWLKAFYDKVAEKLKEAFKVQPYLDDWLKAFYDKVAEKLKEAF-NH2, and (4) Ac-DWLKAFYDKVAEKLKEAFNGGARLADWLKAFYDKVAEKLKEAF-NH2- Surprisingly, peptides 1-3 formed fibrils after incubation (37 degrees C, 10 mM sodium phosphate, pH 7.60), but in contrast to beta-sheet amyloid fibrils, these did not bind thioflavin T and they induced a blue shift in the spectrum of Congo red. CD (peptides 1-3) and FTIR (peptides 1 and 2) of the fibrils showed significant alpha-helical character. Synchrotron X-ray fiber diffraction on a magnetically aligned sample of 1 confirmed the alpha-helical character in the fibrils and indicated that the helical axes are oriented perpendicular to the fibril axis. In contrast, peptide 4, containing two Gly residues but no Pro in the turn, formed only a small amount of nonfibrillar precipitate after prolonged incubation. Peptide V (peptide 4 with a Pro in place of the central Ala) and peptide 5, containing a PEG block in lieu of the central turn, were similar to peptide 4 in not forming fibrils, possibly because the region linking the helices was unstructured. These studies indicate that varying turn sequences between longer amphiphilic alpha-helical segments can drive the structure of fibrils.
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页码:12681 / 12689
页数:9
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