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J Mol Biol. 2010 Mar 26;397(2):408-22. doi: 10.1016/j.jmb.2010.01.030. Epub 2010 Jan 22.

Resonance assignment and three-dimensional structure determination of a human alpha-defensin, HNP-1, by solid-state NMR.

Author information

1
Department of Chemistry, Iowa State University, Ames, IA 50011, USA.

Abstract

Human alpha-defensins [human neutrophil peptides (HNPs)] are immune defense mini-proteins that act by disrupting microbial cell membranes. Elucidating the three-dimensional (3D) structures of HNPs in lipid membranes is important for understanding their mechanisms of action. Using solid-state NMR (SSNMR), we have determined the 3D structure of HNP-1 in a microcrystalline state outside the lipid membrane, which provides benchmarks for structure determination and comparison with the membrane-bound state. From a suite of two-dimensional and 3D magic-angle spinning experiments, (13)C and (15)N chemical shifts that yielded torsion angle constraints were obtained, while inter-residue distances were obtained to restrain the 3D fold. Together, these constraints led to the first high-resolution SSNMR structure of a human defensin. The SSNMR structure has close similarity to the crystal structures of the HNP family, with the exception of the loop region between the first and second beta-strands. The difference, which is partially validated by direct torsion angle measurements of selected loop residues, suggests possible conformational variation and flexibility of this segment of the protein, which may regulate HNP interaction with the phospholipid membrane of microbial cells.

PMID:
20097206
PMCID:
PMC2873975
DOI:
10.1016/j.jmb.2010.01.030
[Indexed for MEDLINE]
Free PMC Article

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