Mirabilis Jalapa Antibacterial Peptides and Raphanus Sativus Antifungal Proteins: A Comparative Study of their Structure and Biological Activities

Abstract

Two peptides with antimicrobial properties (Mj-AMPs) and two proteins with antifungal activity (Rs-AFPs) were isolated from seeds of Mirabilis jalapa L. and Raphanus sativus L., respectively. Both peptides and proteins are highly basic and cysteine-rich. Complete amino acid sequences were determined for the Mj-AMPs (Mj-AMP1 has 37 amino acids and Mj-AMP2 consists of 36 amino acids) and revealed homology to some invertebrata neurotoxins. N-terminal amino acid sequences of Rs-AFPs showed homology with the derived amino acid sequences of two pea genes, induced upon fungal attack, to Γ-thionins from wheat and to α-amylase inhibitors from sorghum. Both Mj-AMPs and Rs-AFPs exhibit a broad spectrum of antifungal activity. The activity of Mj-AMPs and Rs-AFPs is reduced in presence of inorganic cations, but Rs-AFPs (especially Rs-AFP2) are comparitively less sensitive to antagonism by cations. The Mj-AMPs, not the Rs-AFPs are also active against yeast and some Gram-positive bacteria. The viability of cultured human cells is not affected by Mj-AMPs nor by Rs-AFPs. In spray tests both Mj-AMP1 and Rs-AFP2 protect sugar-beet leaves against infection with Cercospora beticola (leaf spot disease).KeywordsAntifungal ActivityRaphanus SativusAntifungal ProteinComplete Amino Acid SequenceLeaf Spot DiseaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.