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J. Biol. Chem., Vol. 275, Issue 35, 26821-26827, September 1, 2000
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From the Department of Biochemistry, University of Illinois College
of Medicine at Urbana-Champaign, Urbana, Illinois 61801
A naturally occurring point mutant of human
apolipoprotein A-I (apoA-I), V156E, which is associated with extremely
low plasma apoA-I and high density lipoprotein (HDL) levels, and
coronary artery disease (Huang, W., Sasaki, J., Matsunaga, A.,
Nanimatsu, H., Moriyama, K., Han, H. Kugi, M., Koga, T., Yamaguchi, K.,
and Arakawa, K. (1998) Arterioscler. Throm. Vasc. Biol. 18, 389-396), was produced in an Escherichia coli expression
system. The purified recombinant proapoA-I V156E mutant was examined in
its structural and functional properties, both, in the lipid-free and
lipid-bound states. In the lipid-free form the mutant protein exhibited
small changes in conformation, but was more stable, and quite resistant to self-association, compared with control apoA-I. The V156E mutant was
able to interact with phospholipid (PL) at high PL:protein ratios
(95:1, mol/mol), but was inefficient in forming reconstituted HDL
(rHDL) complexes at lower PL:protein ratios (40:1). In the lipid-bound,
rHDL state, the mutant protein was somewhat more
A Key Point Mutation (V156E) Affects the Structure and Functions
of Human Apolipoprotein A-I*
-helical and formed
a larger complex (110 Å) than control apoA-I (97 Å). Furthermore, the
rHDL particles containing the V156E mutant did not rearrange to smaller
particles in the presence of low density lipoproteins, and had minimal
reactivity with lecithin-cholesterol acyltransferase (LCAT), compared
with rHDL particles made with control apoA-I. These results suggest a
key role for Val-156, or the adjacent central region of apoA-I in the
modulation of apoA-I conformation, stability, and self-association in
solution, and in the formation of small HDL, the conformational
adaptability of apoA-I leading to structural rearrangements of HDL, and
the activation of LCAT.
*
This work was supported by National Institutes of Health
Grants HL 16059 and HL 29939.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed: Dept. of Biochemistry,
College of Medicine at Urbana-Champaign, University of Illinois, 506 South Mathews Ave., Urbana, IL 61801. Tel.: 217-333-0452; Fax:
217-333-8868; E-mail: a-jonas@uiuc.edu.
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