A novel β-defensin structure: Big defensin changes its N-terminal structure to associate with the target membrane

Takahide Kouno, Mineyuki Mizuguchi, Tomoyasu Aizawa, Hiroyuki Shinoda, Makoto Demura, Shun Ichiro Kawabata, Keiichi Kawano

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Big defensin is a 79-residue peptide derived from hemocytes of the Japanese horseshoe crab. The amino acid sequence of big defensin is divided into an N-terminal hydrophobic domain and a C-terminal cationic domain, which are responsible for antimicrobial activities against Gram-positive and -negative bacteria, respectively. The N-terminal domain of big defensin forms a unique globular conformation with two α-helices and a parallel β-sheet, while the C-terminal domain adopts a β-defensin-like fold. Although our previous study implied that big defensin changes its N-terminal structure in a micellar environment, due to the poor quality of the NMR spectra it remained to be resolved whether the N-terminal domain adopts any structure in the presence of micelles. In this analysis, we successfully determined the structure of the N-terminal fragment of big defensin in a micellar solution, showing that the fragment peptide forms a single α-helix structure. Moreover, NMR experiments using paramagnetic probes revealed that the N-terminal domain of big defensin penetrates into the micelle with a dipping at the N-terminal edge of the α-helix. Here, we propose a model for how big defensin associates with the target membrane.

Original languageEnglish
Pages (from-to)7629-7635
Number of pages7
JournalBiochemistry
Volume48
Issue number32
DOIs
Publication statusPublished - Aug 18 2009

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All Science Journal Classification (ASJC) codes

  • Biochemistry

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