Biocidal proteins

Abstract

Biocidal proteins capable of isolation from seeds have been characterized. The proteins have an amino acid sequence containing the common cysteine/glycine domain of Chitin-binding Plant Proteins but show substantially better activity against pathogenic fungi, a higher ratio of basic amino acids to acidic amino acids, and/or antifungal activity which results in increased hyphal branching. Antimicrobial proteins isolated from Amaranthus, Capsicum, Briza and related species are provided. The proteins show a wide range of antifungal activity and are active against Gram-positive bacteria. DNA encoding the proteins may be isolated and incorporated into vectors. Plants may be transformed with this DNA. The proteins find agricultural or pharmaceutical application as antifungal or antibacterial agents. Transgenic plants expressing the protein will show increased disease resistance.

1 . An isolated DNA sequence encoding a protein comprising -cysteine-cysteine-(serine or threonine)-(one amino acid)-(tryptophan, tyrosine or phenylalanine)-glycine-(tryptophan, tyrosine or phenylalaine)-cysteine-glycine-(SEQ ID NO:21), wherein said protein has a ratio of basic amino acids to acidic amino acids of 5:1, 4:1 or 3:1, and wherein said protein also has antimicrobial and/or antifungal activity, said antifungal activity being at least one order of magnitude greater than the antifungal activity of hevein or nettle lectin.  
     
     
         2 . The isolated DNA sequence as claimed in  claim 1 , wherein said antimicrobial and/or antifungal activity is activity against plant pathogenic fungi resulting in hyphal branching.  
     
     
         3 . A vector containing a DNA sequence as claimed in  claim 1 .  
     
     
         4 . A vector containing a DNA sequence as claimed in  claim 2 .  
     
     
         5 . A biological system including an isolated DNA sequence as claimed in  claim 1 .  
     
     
         6 . A biological system including an isolated DNA sequence as claimed in  claim 2 .  
     
     
         7 . The biological system of  claim 5  which is selected from the group consisting of a micro-organism, a cultured insect cell, a cultured mammalian cell and a plant cell.  
     
     
         8 . The biological system of  claim 6  which is selected from the group consisting of a micro-organism, a cultured insect cell, a cultured mammalian cell and a plant cell.  
     
     
         9 . An isolated DNA sequence as claimed in  claim 1  wherein said protein comprises a central motif of -cysteine-(four amino acids)-cysteine-cysteine (serine or threonine)-(one amino acid)-(tryptophan, tyrosine or phenylalanine)-glycine-(tryptophan, tyrosine or phenylalanine)-cysteine-glycine (five amino acids)-cysteine-(six amino acids)-cysteine-(SEQ ID No. 22).