Purification and partial characterization of figaren, an RNase-like novel antiviral protein from Cucumis figarei

An antiviral protein, designated figaren, was purified from leaves of Cucumis figarei and partially characterized. Column chromatography, SDS-polyacrylamide gel electrophoresis and periodic acid-Schiff staining revealed that figaren is a glycoprotein with a molecular weight of 23 kDa. Figaren was stable at pH 2 to 12 and below 90 deg C. N-termmal amino acid sequencing indicated that figaren contained the conserved region for the S-allele-associated ribonucleases (RNases). In-gel RNase assay showed that figaren digested yeast RNAs. Figaren also digested double-stranded RNAs extracted from Cucumber mosaic virus (CMV)-infected tobacco tissues. Fluorescence in situ hybridization revealed that figaren and RNases (beef pancrease and RNase T sub(1) at 1 micro g /ml similarly inhibited CMV infection in cowpea leaves. Figaren and the RNases at 5 - 500 ng /ml had similar inhibitory effect on local lesion formation by CMV. These data suggest that figaren is a novel RNase-like antiviral protein.