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标题：ADP-ribosylation of human defensin HNP-1 results in the replacement of the modified arginine with the noncoded amino acid ornithine
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作者：Linda A. Stevens ; Rodney L. Levine ; Bernadette R. Gochuico 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：47
页码：19796-19800
DOI：10.1073/pnas.0910633106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Defensins (e.g., human neutrophil peptides, or HNPs) contribute to innate immunity through diverse actions, including microbial killing; high concentrations are present in the lung in response to inflammation. Arginines are critical for HNP activity, which is decreased by their replacement with ornithine. ADP-ribosyltransferases (ARTs) catalyze transfer of ADP-ribose from NAD to an acceptor arginine in a protein substrate, whereas ADP-ribosylarginine hydrolases release ADP-ribose. ART1 on the surface of airway epithelial cells ADP-ribosylated HNP-1 specifically on arginines 14 and 24, with ADP-ribosylation altering biological activity. Di- and mono-ADP-ribosylated HNP-1 were isolated from bronchoalveolar lavage fluid (BALF) of patients with asthma and idiopathic pulmonary fibrosis (IPF), suggesting a role for ADP-ribosylation in disease. In the present study, we observed that ART1-catalyzed ADP-ribosylation of HNP-1 in vitro generated a product with ADP-ribose on arginine 24, and ornithine replacing arginine at position 14. We hypothesized that ADP-ribosylarginine is susceptible to a nonenzymatic hydrolytic reaction yielding ornithine. On incubation of di- or mono-ADP-ribosyl-HNP-1 at 37 {degrees}C, ADP-ribosylarginine was partially replaced by ornithine, whereas ornithine was not detected by amino acid analysis and mass spectrometry of unmodified HNP-1 incubated under the same conditions. Further, ornithine was produced from the model compound, ADP-ribosylarginine. BALF from an IPF patient contained ADP-ribosyl-HNP-ornithine as well as mono- and di-ADP-ribosylated HNP-1, consistent with in vivo conversion of arginine to ornithine. Targeted ADP-ribosylation of specific arginines by transferases, resulting in their replacement with ornithine, is an alternative pathway for regulation of protein function through posttranslational modification.
关键词：posttranslational modification ; NAD ; bacterial toxins