Type 1 Ribosome-Inactivating Proteins from the Ombu Tree (Phytolacca dioica L.)

The toxicity of plant proteins, later identified as ribosome-inactivating proteins (RIPs), was described more than a century ago and their enzymatic activity was established more than 30 years ago. However, their physiological role and related biological activities are still uncertain. Therefore, despite the body of literature, research on RIPs is ongoing. This review deals with new RIPs being purified, sequenced, characterized, and cloned, and an increasing number of 3D-structures that are determined at high resolution. This is the case of the five type 1 RIPs (PD-S1-3, PD-L1/2, PD-L3/4, dioicin 1, and dioicin 2) from seeds and leaves of the ombu tree (Phytolacca dioica L.), native of the grassy pampas of Argentina. The data collected so far will contribute to our understanding of important issues of RIP research: (1) identifying structural determinants responsible for new enzymatic activities such as the DNA cleaving activity; (2) glycosylation and its influence on the catalytic and biological activities; (3) cellular localization of endogenous RIPs and their physiological role(s).