Deletion of single amino acid E235 affects the structure and lipid interaction of human apolipoprotein A-I C-terminal peptides.
The C-terminal domain of apolipoprotein (apo) A-I plays an important role in lipid binding. ApoA-I Nichinan, a naturally occurring human apoA-I variant with a deletion of E235 located in the C-terminus, is associated with low high-density lipoprotein (HDL) cholesterolemia. In the present study, a series of variant peptides corresponding to residues 220-241 of human apoA-I were examined to clarify the influences of E235 deletion (DeltaE235) on the structure and lipid interaction of the C-terminal region. NMR studies demonstrated that in trifluoroethanol, apoA-I 220-241/DeltaE235 peptide forms the alpha-helical structure similar to wild-type (WT) peptide. Circular dichroism measurements revealed that the interaction with phospholipid vesicles induced structural changes from random coil to alpha-helix both in apoA-I 220-241 WT and E235A, a variant with a negative charge ablation, peptides. These peptides also showed abilities to form HDL-like particles through microsolubilization of phospholipid vesicles, indicating that the negative charge ablation in E235 has no effect on the lipid interaction. By contrast, neither lipid binding-induced alpha-helix formation nor microsolubilization of vesicles were observed in apoA-I 220-241/DeltaE235 and L230P, a helix-breaking variant, peptides. In addition, fluorescence measurements showed that tryptophan fluorescence intensity of apoA-I 220-241/F225W greatly increased upon lipid binding, while only a little increase was observed for the corresponding DeltaE235 variant. Taken together, these results suggest that the deletion of E235 causes defective lipid binding of apoA-I Nichinan because of the impaired helix-forming ability of the C-terminal residues.
Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe, Hyogo, Japan.
Toshitaka
T
Tanaka
Masafumi
M
Tanaka
Makiko
M
Sugiura
Toru
T
Kawakami
Saburo
S
Aimoto
Hiroyuki
H
Saito
D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D017353:Gene Deletion; D018698:Glutamic Acid / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008055:Lipids / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
D016632:Apolipoprotein A-I; D008055:Lipids; D010446:Peptide Fragments; D018698:Glutamic Acid