Cofactor requirement of ribosome-inactivating proteins from plants

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 requirement for ATP and supernatant factors for full activity. A marked requirement was observed with agrostin among Caryophyllaceae, gelonin among Euphorbiaceae, and with both barley RIP and tritin-S among Poaceae. The distribution of cofactor requirement in Phytolaccaceae discriminates leaf forms (cofactor-independent) from seed and root forms (cofactor-dependent). The results are discussed on the basis of the present knowledge on the tissue localization of RIPs and on the sensitivity of ribosomes to conspecific RIPs.