Hormonotoxins: Abrogation of ribosome inactivating property of gelonin in the disulfide linked ovine luteinizing hormone-gelonin conjugates

In order to synthesize a bioeffective hormonotoxin for selective targeting to specific cells in the gonads, gelonin, a single chain ribosome-inactivating protein obtained from an Indian plant called Gelonium multiflorum was covalently linked to ovine luteinizing hormone (oLH) by a disulfide bond. Ovine LH-S-S-gelonin conjugates of different molar ratios were subjected to determine the ribosome-inactivating property in a cell-free translation assay using rabbit reticulocyte lysate system. A single amino group modification with N-succinimidyl-3-(2-pyridyldithio)propionate resulted in a loss of 90% protein synthesis inhibition activity. Upon conjugation of gelonin to oLH, the activity was further inhibited ranging from 2.5 - 6.4%. A 1:1 to 1:1.5 molar ratio (oLH-S-S-gelonin) conjugates showed 2.5 - 4.6% activity while 1:2.8 to 1:2.2 molar ratio exhibited 5.5 - 6.4% inhibition ability.