Structural basis for the conformational adaptability of apolipophorin III, a helix-bundle exchangeable apolipoproteinWang, J., Sykes, B.D., Ryan, R.O.
(2002) Proc Natl Acad Sci U S A 99: 1188-1193
- PubMed: 11818551
- DOI: https://doi.org/10.1073/pnas.032565999
- Primary Citation of Related Structures:
- PubMed Abstract:
The high-resolution NMR structure of apolipophorin III from the sphinx moth, Manduca sexta, has been determined in the lipid-free state. We show that lipid-free apolipophorin III adopts a unique helix-bundle topology that has several characteristic structural features. These include a marginally stable, up-and-down helix bundle that allows for concerted opening of the bundle about "hinged" loops upon lipid interaction and buried polar/ionizable residues and buried interhelical H-bonds located in the otherwise hydrophobic interior of the bundle that adjust protein stability and facilitate lipid-induced conformational opening. We suggest that these structural features modulate the conformational adaptability of the lipid-free helix bundle upon lipid binding and control return of the open conformation to the original lipid-free helix-bundle state. Taken together, these data provide a structural rationale for the ability of exchangeable apolipoproteins to reversibly interact with circulating lipoprotein particles.
Department of Biochemistry and Molecular Biology, School of Medicine, Southern Illinois University, Carbondale, IL 62901-4413, USA. firstname.lastname@example.org