The helix-hinge-helix structural motif in human apolipoprotein A-I determined by NMR spectroscopy

Guangshun Wang, James T. Sparrow, Robert J. Cushley

Research output: Contribution to journalArticle

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Abstract

The conformation of a synthetic peptide of 46 residues from apoA-I was investigated by fluorescence, CD, and 2D NMR spectroscopies in lipid-mimetic environments. ApoA-I(142-187) is mainly unstructured in water but helical in SDS or dodecylphosphocholine (DPC), although the peptide only associates with DPC at approximately the critical micellar concentration. Solution structures of apoA-I(142-187) were determined by distance geometry calculations based on 450 (in DPC-d38) or 397 (in SDS-d25) NOE-derived distance restraints, respectively. Backbone RMSDs for superimposing the two helical regions 146- 162 and 168-182 are 0.98 ± 0.22 (2.38 ± 0.20) and 1.99 ± 0.42 (2.02 ± 0.21) Å in DPC (SDS), respectively. No interhelical NOE was found, suggesting that helix-helix interactions between the two helical domains in apoA-I(142-187) are unlikely. Similar average, curved helix-hinge-helix structures were found in both SDS and DPC micelles with the hydrophobic residues occupying the concave face, indicating that hydrophobic interactions dominate. Intermolecular NOESY experiments, performed in the presence of 50% protonated SDS, confirm that the two amphipathic helices and Y166 in the hinge all interact with the micelle. The involvement of Y166 in lipid binding is supported by fluorescence spectroscopy as well. On the basis of all the data above, we propose a model for the peptide-lipid complexes wherein the curved amphipathic helix-hinge-helix structural motif straddles the micelle. The peptide-aided signal assignment achieved for apoA-I(122-187) (66mer) and apoA-I suggests that such a structural motif is retained in the longer peptide and most likely in the intact protein.

Original languageEnglish (US)
Pages (from-to)13657-13666
Number of pages10
JournalBiochemistry
Volume36
Issue number44
DOIs
StatePublished - Nov 4 1997

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Apolipoprotein A-I
Hinges
Nuclear magnetic resonance spectroscopy
Magnetic Resonance Spectroscopy
Micelles
Peptides
Lipids
Fluorescence Spectrometry
Fluorescence spectroscopy
Protein Sorting Signals
Hydrophobic and Hydrophilic Interactions
Conformations
human APOA1 protein
Fluorescence
dodecylphosphocholine
Geometry
Water
Proteins
Experiments

ASJC Scopus subject areas

  • Biochemistry

Cite this

The helix-hinge-helix structural motif in human apolipoprotein A-I determined by NMR spectroscopy. / Wang, Guangshun; Sparrow, James T.; Cushley, Robert J.

In: Biochemistry, Vol. 36, No. 44, 04.11.1997, p. 13657-13666.

Research output: Contribution to journalArticle

Wang, Guangshun ; Sparrow, James T. ; Cushley, Robert J. / The helix-hinge-helix structural motif in human apolipoprotein A-I determined by NMR spectroscopy. In: Biochemistry. 1997 ; Vol. 36, No. 44. pp. 13657-13666.
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abstract = "The conformation of a synthetic peptide of 46 residues from apoA-I was investigated by fluorescence, CD, and 2D NMR spectroscopies in lipid-mimetic environments. ApoA-I(142-187) is mainly unstructured in water but helical in SDS or dodecylphosphocholine (DPC), although the peptide only associates with DPC at approximately the critical micellar concentration. Solution structures of apoA-I(142-187) were determined by distance geometry calculations based on 450 (in DPC-d38) or 397 (in SDS-d25) NOE-derived distance restraints, respectively. Backbone RMSDs for superimposing the two helical regions 146- 162 and 168-182 are 0.98 ± 0.22 (2.38 ± 0.20) and 1.99 ± 0.42 (2.02 ± 0.21) {\AA} in DPC (SDS), respectively. No interhelical NOE was found, suggesting that helix-helix interactions between the two helical domains in apoA-I(142-187) are unlikely. Similar average, curved helix-hinge-helix structures were found in both SDS and DPC micelles with the hydrophobic residues occupying the concave face, indicating that hydrophobic interactions dominate. Intermolecular NOESY experiments, performed in the presence of 50{\%} protonated SDS, confirm that the two amphipathic helices and Y166 in the hinge all interact with the micelle. The involvement of Y166 in lipid binding is supported by fluorescence spectroscopy as well. On the basis of all the data above, we propose a model for the peptide-lipid complexes wherein the curved amphipathic helix-hinge-helix structural motif straddles the micelle. The peptide-aided signal assignment achieved for apoA-I(122-187) (66mer) and apoA-I suggests that such a structural motif is retained in the longer peptide and most likely in the intact protein.",
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AB - The conformation of a synthetic peptide of 46 residues from apoA-I was investigated by fluorescence, CD, and 2D NMR spectroscopies in lipid-mimetic environments. ApoA-I(142-187) is mainly unstructured in water but helical in SDS or dodecylphosphocholine (DPC), although the peptide only associates with DPC at approximately the critical micellar concentration. Solution structures of apoA-I(142-187) were determined by distance geometry calculations based on 450 (in DPC-d38) or 397 (in SDS-d25) NOE-derived distance restraints, respectively. Backbone RMSDs for superimposing the two helical regions 146- 162 and 168-182 are 0.98 ± 0.22 (2.38 ± 0.20) and 1.99 ± 0.42 (2.02 ± 0.21) Å in DPC (SDS), respectively. No interhelical NOE was found, suggesting that helix-helix interactions between the two helical domains in apoA-I(142-187) are unlikely. Similar average, curved helix-hinge-helix structures were found in both SDS and DPC micelles with the hydrophobic residues occupying the concave face, indicating that hydrophobic interactions dominate. Intermolecular NOESY experiments, performed in the presence of 50% protonated SDS, confirm that the two amphipathic helices and Y166 in the hinge all interact with the micelle. The involvement of Y166 in lipid binding is supported by fluorescence spectroscopy as well. On the basis of all the data above, we propose a model for the peptide-lipid complexes wherein the curved amphipathic helix-hinge-helix structural motif straddles the micelle. The peptide-aided signal assignment achieved for apoA-I(122-187) (66mer) and apoA-I suggests that such a structural motif is retained in the longer peptide and most likely in the intact protein.

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