In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 24 ( 1996-11-26), p. 13605-13610
Kurzfassung:
Apolipoprotein AI (apoAI) is the principal protein constituent of
high density lipoproteins and it plays a key role in human cholesterol homeostasis; however, the structure of apoAI is not clearly understood.
To test the hypothesis that apoAI is organized into domains, three deletion mutants of human apoAI expressed in Escherichia
coli were studied in solution and in reconstituted high density
lipoprotein particles. Each mutant lacked one of three specific regions that together encompass almost the entire 243 aa sequence of native
apoAI ( apoAI Δ44-126 , apoAI Δ139-170 ,
and apoAI Δ190-243 ). Circular dichroism spectroscopy
showed that the α-helical content of lipid-free apoAI Δ44-126 was 27% while the other mutants and native apoAI averaged 55 ± 2%,
suggesting that the missing N-terminal portion contains most of the α-helical structure of lipid-free apoAI. ApoAI Δ44-126 exhibited
the largest increase in α-helix upon lipid binding (125% increase versus an average of 25% for the others), confirming the importance of
the C-terminal half of apoAI in lipid binding. Denaturation studies showed that the N-terminal half of apoAI is primarily responsible for
α-helix stability in the lipid-free state, whereas the C terminus is required for α-helix stability when lipid-bound. We conclude that the
N-terminal half (aa 44–126) of apoAI is responsible for most of the α-helical structure and the marginal stability of lipid-free apoAI
while the C terminus (aa 139–243) is less organized. The increase in α-helical content observed when native apoAI binds lipid results from
the formation of α-helix primarily in the C-terminal half of the molecule.
Materialart:
Online-Ressource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.93.24.13605
Sprache:
Englisch
Verlag:
Proceedings of the National Academy of Sciences
Publikationsdatum:
1996
ZDB Id:
209104-5
ZDB Id:
1461794-8
SSG:
11
SSG:
12
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