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International Journal of Peptides
Volume 2011 (2011), Article ID 594723, 7 pages
Review Article

Structural and Functional Consequences Induced by Post-Translational Modifications in α-Defensins

1School of Biosciences and Biotechnologies, University of Camerino, Gentile III da Varano Street, 62032 Camerino, Italy
2Department of Chemistry, University of Siena, 53100 Siena, Italy
3Research Center, Novartis, Fiorentina 1 Street, 53100 Siena, Italy
4Department of Evolutionary Biology, University of Siena, 53100 Siena, Italy

Received 3 April 2011; Accepted 22 May 2011

Academic Editor: Peter Bergman

Copyright © 2011 Enrico Balducci et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


HNP-1 is an antimicrobial peptide that undergoes proteolytic cleavage to become a mature peptide. This process represents the mechanism commonly used by the cells to obtain a fully active antimicrobial peptide. In addition, it has been recently described that HNP-1 is recognized as substrate by the arginine-specific ADP-ribosyltransferase-1. Arginine-specific mono-ADP-ribosylation is an enzyme-catalyzed post-translational modification in which NAD+ serves as donor of the ADP-ribose moiety, which is transferred to the guanidino group of arginines in target proteins. While the arginine carries one positive charge, the ADP-ribose is negatively charged at the phosphate moieties at physiological pH. Therefore, the attachment of one or more ADP-ribose units results in a marked change of cationicity. ADP-ribosylation of HNP-1 drastically reduces its cytotoxic and antibacterial activities. While the chemotactic activity of HNP-1 remains unaltered, its ability to induce interleukin-8 production is enhanced. The arginine 14 of HNP-1 modified by the ADP-ribose is in some cases processed into ornithine, perhaps representing a different modality in the regulation of HNP-1 activities.