Chemical Modification And Spectral Researches Of RIPS (Curcin)

Ribosome-inactivating proteins (RIPs)from plants catalyze the seletive hydrolysis of the N-glycosidic bond at the adenine-4324 residue in the eukaryotic 28S ribosomal RNA .Based on their primary structures, RIPs can be classified into three types. Type 1 RIPs consist of single peptide chain with a molecular mass varying from 10 to 30 kDa. The most remarkable character of type 1 RIPs is the strong translation -inhibitory function to the cell-free system, and the N-glycosidase activity of the single A-chain can be monitored with in vitro translation assays using the rabbit reticulocyte lysate system.Our laboratory has purified a type 1 RIPs, called curcin. The research work about the gene clone and sequence analysis have done, but still know little about the senior stucture information. In order to know more about the relation between the sructure and inhibitory activity, the paper discussed the results of the chemical modification to the 5 types of amoni acids.Curcin was isolated from the seeds of JATROPHA CURCAS by extraction, precipitation with (NH₄)₂SO₄, gel filtration on Sephadex G-100. The purified curcin showed a single protein band on SDS-PAGE.The effects of modifying the amino acids in Jatropha curcas RIPs (curcin) on the conformation and activity of curcin were studied by cell-free translation-inhibitory activity assay, fluorescence and circular dichroism record. The results indicate that the modification of cysteine and histidine residues has no effect on the activity. The modification of lysine and...