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J Biol Chem. 2016 Mar 4;291(10):5439-51. doi: 10.1074/jbc.M115.706093. Epub 2016 Jan 11.

An Evaluation of the Crystal Structure of C-terminal Truncated Apolipoprotein A-I in Solution Reveals Structural Dynamics Related to Lipid Binding.

Author information

1
From the Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237.
2
the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45237.
3
the Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294.
4
the Laboratory for Proteomics and Protein Engineering, Carlos Chagas Institute, Fiocruz, Paraná, Brazil 81350-010, and.
5
the Dalton Mass Spectrometry Laboratory, University of Campinas, São Paulo 13083-970, Brazil.
6
the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45237, Tom.Thompson@uc.edu.
7
From the Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45237, Sean.Davidson@UC.edu.

Abstract

Apolipoprotein (apo) A-I mediates many of the anti-atherogenic functions attributed to high density lipoprotein. Unfortunately, efforts toward a high resolution structure of full-length apoA-I have not been fruitful, although there have been successes with deletion mutants. Recently, a C-terminal truncation (apoA-I(Δ185-243)) was crystallized as a dimer. The structure showed two helical bundles connected by a long, curved pair of swapped helical domains. To compare this structure to that existing under solution conditions, we applied small angle x-ray scattering and isotope-assisted chemical cross-linking to apoA-I(Δ185-243) in its dimeric and monomeric forms. For the dimer, we found evidence for the shared domains and aspects of the N-terminal bundles, but not the molecular curvature seen in the crystal. We also found that the N-terminal bundles equilibrate between open and closed states. Interestingly, this movement is one of the transitions proposed during lipid binding. The monomer was consistent with a model in which the long shared helix doubles back onto the helical bundle. Combined with the crystal structure, these data offer an important starting point to understand the molecular details of high density lipoprotein biogenesis.

KEYWORDS:

apolipoprotein; mass spectrometry (MS); oligomerization; small-angle x-ray scattering (SAXS); structural biology; structural model

PMID:
26755744
PMCID:
PMC4777873
DOI:
10.1074/jbc.M115.706093
[Indexed for MEDLINE]
Free PMC Article

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