A Novel Family of Small Cysteine-rich Antimicrobial Peptides from Seed of Impatiens balsaminaIs Derived from a Single Precursor Protein

Abstract

Four closely related peptides were isolated from seed of Impatiens balsamina and were shown to be inhibitory to the growth of a range of fungi and bacteria, while not being cytotoxic to cultured human cells. The peptides, designated Ib-AMP1, Ib-AMP2, Ib-AMP3, and Ib-AMP4, are 20 amino acids long and are the smallest plant-derived antimicrobial peptides isolated to date. The IbAMPs (I. balsamina antimicrobial peptides) are highly basic and contain four cysteine residues which form two intramolecular disulfide bonds. Searches of protein data bases have failed to identify any proteins with significant homology to the peptides described here. Characterization of isolated cDNAs reveals that all four peptides are encoded within a single transcript. The predicted Ib-AMP precursor protein consists of a prepeptide followed by 6 mature peptide domains, each flanked by propeptide domains ranging from 16 to 35 amino acids in length. Such a primary structure with repeated alternating basic mature peptide domains and acidic propeptide domains has, to date, not been reported in plants.

Discovery of Linear Cyclotides in Monocot Plant Panicum laxum of Poaceae Family Provides New Insights into Evolution and Distribution of Cyclotides in Plants

“…It is uncertain whether this N-terminal modification occurs spontaneously or is catalyzed by a specific glutamyl cyclase. Similar modifications have been identified in a number of plant peptides such as Phyb M isolated from P. hybrida (15), squash trypsin inhibitors from Cucurbitaceae plants (19,39), and Ib-AMP from Impatiens balsamina (40). The incorporation of an N-terminal pyroGlu residue in panitides may be an alternative strategy to the backbone cyclization to provide protection against exopeptidase degradation.…”

Specific, High Affinity Binding Sites for an Antifungal Plant Defensin on Neurospora crassa Hyphae and Microsomal Membranes

“…Rs-AFP2, Ace-AMP1, Ac-AMP1, Mj-AMP2, and Ib-AMP4 were isolated as described previously by Terras et al (3), Cammue et al (12), Broekaert et al (13), Cammue et al (14), and Tailor et al (15), respectively. Rs-AFP2(Y38G) was purified from the culture medium of recombinant yeast (Saccharomyces cerevisiae) as described previously by De Samblanx et al (11).…”

A phyto-pharmacological overview on Jewel Weed

“…Peptides were inhibitory to the fungai and bacterial growth and were no cytotoxic to cultured human cells (Tailor et al, 1997). Further synthetic variant of Ib-AMP1 was found to be fully active on yeast and fungal strains.…”