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Journal of Bacteriology, August 2003, p. 4938-4947, Vol. 185, No. 16
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.16.4938-4947.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Conformation of a Bactericidal Domain of Puroindoline a: Structure and Mechanism of Action of a 13-Residue Antimicrobial Peptide

Weiguo Jing, Alistair R. Demcoe, and Hans J. Vogel^*

Structural Biology Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada

Received 31 January 2003/ Accepted 23 May 2003

Puroindoline a, a wheat endosperm-specific protein containing a tryptophan-rich domain, was reported to have antimicrobial activities. We found that a 13-residue fragment of puroindoline a (FPVTWRWWKWWKG-NH₂) (puroA) exhibits activity against both gram-positive and gram-negative bacteria. This suggests that puroA may be a bactericidal domain of puroindoline a. PuroA interacted strongly with negatively charged phospholipid vesicles and induced efficient dye release from these vesicles, suggesting that the microbicidal effect of puroA may be due to interactions with bacterial membranes. A variety of biophysical and biochemical methods, including fluorescence spectroscopy and microcalorimetry, were used to examine the mode of action of puroA. These studies showed that puroA is located at the membrane interface, probably due to its high content of Trp residues that have a high propensity to partition into the membrane interface. The penetration of these Trp residues in negatively charged phospholipid vesicles resembling bacterial membranes was more extensive than the penetration in neutral vesicles mimicking eukaryotic membranes. Peptide binding had a significant influence on the phase behavior of the former vesicles. The three-dimensional structure of micelle-bound puroA determined by two-dimensional nuclear magnetic resonance spectroscopy indicated that all the positively charged residues are oriented close to the face of Trp indole rings, forming energetically favorable cation- interactions. This characteristic, along with its well-defined amphipathic structure upon binding to membrane mimetic systems, allows puroA to insert more deeply into bacterial membranes and disrupt the regular membrane bilayer structure.

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* Corresponding author. Mailing address: Structural Biology Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada. Phone: (403) 220-6006. Fax: (403) 289-9311. E-mail: vogel{at}ucalgary.ca.

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Journal of Bacteriology, August 2003, p. 4938-4947, Vol. 185, No. 16
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.16.4938-4947.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Li, W., Huang, L., Gill, B. S. (2008). Recurrent Deletions of Puroindoline Genes at the Grain Hardness Locus in Four Independent Lineages of Polyploid Wheat1,[W],[OA]. Plant Physiol. 146: 200-212 [Abstract] [Full Text]  
• Wei, S.-Y., Wu, J.-M., Kuo, Y.-Y., Chen, H.-L., Yip, B.-S., Tzeng, S.-R., Cheng, J.-W. (2006). Solution Structure of a Novel Tryptophan-Rich Peptide with Bidirectional Antimicrobial Activity. J. Bacteriol. 188: 328-334 [Abstract] [Full Text]