In:
The FEBS Journal, Wiley, Vol. 273, No. 3 ( 2006-02), p. 558-567
Abstract:
The N‐terminal domain of human apolipoprotein E (apoE‐NT) harbors residues critical for interaction with members of the low‐density lipoprotein receptor (LDLR) family. Whereas lipid free apoE‐NT adopts a stable four‐helix bundle conformation, a lipid binding induced conformational adaptation is required for manifestation of LDLR binding ability. To investigate the structural basis for this conformational change, the short helix connecting helix 1 and 2 in the four‐helix bundle was replaced by the sequence NPNG, introducing a β‐turn. Recombinant helix‐to‐turn (HT) variant apoE3‐NT was produced in Escherichia coli , isolated and characterized. Stability studies revealed a denaturation transition midpoint of 1.9 m guanidine hydrochloride for HT apoE3‐NT vs. 2.5 m for wild‐type apoE3‐NT. Wild‐type and HT apoE3‐NT form dimers in solution via an intermolecular disulfide bond. Native PAGE showed that reconstituted high‐density lipoprotein prepared with HT apoE3‐NT have a diameter in the range of 9 nm and possess binding activity for the LDLR on cultured human skin fibroblasts. In phospholipid vesicle solubilization assays, HT apoE3‐NT was more effective than wild‐type apoE3‐NT at inducing a time dependent decrease in dimyristoylphosphatidylglycerol vesicle light scattering intensity. In lipoprotein binding assays, HT apoE3‐NT protected human low‐density lipoprotein from phospholipase C induced aggregation to a greater extent that wild‐type apoE3‐NT. The results indicate that a mutation at one end of the apoE3‐NT four‐helix bundle markedly enhances the lipid binding activity of this protein. In the context of lipoprotein associated full‐length apoE, increased lipid binding affinity of the N‐terminal domain may alter the balance between receptor‐active and ‐inactive conformational states.
Type of Medium:
Online Resource
ISSN:
1742-464X
,
1742-4658
DOI:
10.1111/ejb.2006.273.issue-3
DOI:
10.1111/j.1742-4658.2005.05089.x
Language:
English
Publisher:
Wiley
Publication Date:
2006
detail.hit.zdb_id:
2172518-4
SSG:
12
