Dianthins, ribosome-damaging proteins with anti-viral properties from Dianthus caryophyllus L. (carnation)

1. Dianthin 30 and dianthin 32, two proteins isolated from the leaves of Diathus caryophyllus (carnation), were purified to homogeneity by chromatography on CM-cellulose. 2. The mol.wt. of dianthin 30 is 29 500 and that of dianthin 32 is 31 700. Both dianthins are glycoproteins containing mannose. 3. Dianthins inhibit protein synthesis in a lysate of rabbit reticulocytes, with an ID50 (concentration giving 50% inhibition) of 9.15 ng/ml (dianthin 30) and 3.6 ng/ml (dianthin 32). They act by damaging ribosomes in a less-than-equimolar ratio. Protein synthesis by intact cells is partially inhibited by dianthins at a concentration of 100 microgram/ml. 4. Dianthins mixed with tobacco-mosaic virus strongly decrease the number of local lesions on leaves of Nicotiana glutinosa.