| Abstract: | A large number of type 1 ribosome-inactivating proteins (RIPs)from plants (families of Caryophyllaceae, Cucurbitaceae, Euphorbiaceae,Phytolaccaceae, and Poaceae) were examined for their requirementfor ATP and supernatant factors for full activity. A markedrequirement was observed with agrostin among Caryophyllaceae,gelonin among Euphorbiaceae, and with both barley RIP and tritin-Samong Poaceae. The distribution of cofactor requirement in Phytolaccaceaediscriminates leaf forms (cofactor-independent) from seed androot forms (cofactor-dependent). The results are discussed onthe basis of the present knowledge on the tissue localizationof RIPs and on the sensitivity of ribosomes to conspecific RIPs. Key words: Cofactors, ribosome-inactivating proteins, RNA-N-glycosidase, up-regulation |
