1ls4
From Proteopedia
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NMR structure of apolipophorin-III from Locusta migratoria
Overview
We report here the NMR structure and backbone dynamics of an exchangeable, apolipoprotein, apoLp-III, from the insect Locusta migratoria. The NMR, structure adopts an up-and-down elongated five-helix bundle, which is, similar to the x-ray crystal structure of this protein. A short helix, helix 4', is observed that is perpendicular to the bundle and fully, solvent-exposed. NMR experimental parameters confirm the existence of this, short helix, which is proposed to serve as a recognition helix for, apoLp-III binding to lipoprotein surfaces. The L. migratoria apoLp-III, helix bundle displays several characteristic structural features that, regulate the reversible lipoprotein binding activity of apoLp-III. The, buried hydrophilic residues and exposed hydrophobic residues readily, adjust the marginal stability of apoLp-III, facilitating the helix bundle, opening. Specifically, upon lipoprotein binding the locations and, orientations of the buried hydrophilic residues modulate the apoLp-III, helix bundle to adopt a possible opening at the hinge that is opposite the, recognition short helix, helix 4'. The backbone dynamics provide, additional support to the recognition role of helix 4' and this preferred, conformational adaptation of apoLp-III upon lipid binding. In this case, the lipid-bound open conformation contains two lobes linked by hinge, loops. One lobe contains helices 2 and 3, and the other lobe contains, helices 1, 4, and 5. This preferred bundle opening is different from the, original proposal on the basis of the x-ray crystal structure of this, protein (Breiter, D. R., Kanost, M. R., Benning, M. M., Wesenberg, G., Law, J. H., Wells, M. A., Rayment, I., and Holden, H. M. (1991), Biochemistry 30, 603-608), but it efficiently uses helix 4' as the, recognition short helix. The buried interhelical H-bonds are found to be, mainly located between the two lobes, potentially providing a specific, driving force for the helix bundle recovery of apoLp-III from the, lipid-bound open conformation. Finally, we compare the NMR structures of, Manduca sexta apoLp-III and L. migratoria apoLp-III and present a united, scheme for the structural basis of the reversible lipoprotein binding, activity of apoLp-III.
About this Structure
1LS4 is a Single protein structure of sequence from Locusta migratoria. Full crystallographic information is available from OCA.
Reference
NMR solution structure and dynamics of an exchangeable apolipoprotein, Locusta migratoria apolipophorin III., Fan D, Zheng Y, Yang D, Wang J, J Biol Chem. 2003 Jun 6;278(23):21212-20. Epub 2003 Mar 4. PMID:12621043
Page seeded by OCA on Tue Nov 20 20:49:47 2007
