Truncation of the amino terminus of human apolipoprotein A-I substantially alters only the lipid-free conformation

被引:111
作者
Rogers, DP
Brouillette, CG
Engler, JA
Tendian, SW
Roberts, L
Mishra, VK
Anantharamaiah, GM
LundKatz, S
Phillips, MC
Ray, MJ
机构
[1] UNIV ALABAMA, DEPT MOL GENET & BIOCHEM, BIRMINGHAM, AL 35294 USA
[2] UNIV ALABAMA, DEPT MED, BIRMINGHAM, AL 35294 USA
[3] UNIV ALABAMA, ATHEROSCLEROSIS RES UNIT, BIRMINGHAM, AL 35294 USA
[4] SO RES INST, DEPT BIOCHEM, BIRMINGHAM, AL 35209 USA
[5] CALIF STATE UNIV SACRAMENTO, DEPT CHEM, SACRAMENTO, CA 95819 USA
[6] MED COLL PENN & HAHNEMANN UNIV, DEPT BIOCHEM, PHILADELPHIA, PA 19129 USA
关键词
D O I
10.1021/bi961876e
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
An amino-terminal deletion mutant (residues 1-43) of human apolipoprotein A-I (ape hA-I) has been produced from a bacterial expression system to explore the structural and functional role of these amino acids, encoded by exon 3, in apo hA-I. Lipid binding of apo Delta(1-43)A-I and lipid binding of apo hA-I are very similar as assessed by surface activity, lipid association with palmitoyloleoylphosphatidylcholine (POPC) vesicles, and lipid association with plasma lipoproteins, Preliminary kinetic measurements appear to show that the reactivity of lecithin:cholesterol acyltransferase (LCAT) with the mutant is slightly decreased compared to wild-type apo hA-I. Collectively, these results indicate that the N-terminal region is not necessary for lipid binding or activation of LCAT. In contrast, there are significant structural differences between lipid-free apo Delta(1-43)A-I and apo hA-I, as judged by denaturant-induced unfolding, binding of the fluorescent probe 1-anilinonaphthalene-8-sulfonate, surface balance measurements, and far- and near-ultraviolet circular dichroic spectroscopy. All spectral and physical measurements indicate apo Delta(1-43)A-I has a folded, tertiary structure, although it is significantly less stable than that of apo hA-I. It is concluded that the N-terminal 43 residues are an important structural element of the lipid-free conformational state of apo hA-I, the absence of which induces a fundamentally different fold for the remaining carboxy-terminal residues, compared to those in native apo hA-I.
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页码:288 / 300
页数:13
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