Type I Ribosome-Inactivating Proteins from Saponaria officinalis

Saporins are ribosome-inactivating proteins (RIPs) extracted from different tissues of the soapwort plant (Saponaria officinalis L.). While the biosynthesis of these proteins and their roles in planta have received little attention, saporins have been extensively used for the production of targeted toxins for therapeutical and research applications. The biochemical features of one group of closely related saporin isoforms, collectively named SO6, have been characterized in considerable detail. In this chapter, we summarize available information on the saporin family of proteins, including their catalytic activity, 3D-structure, and biosynthetic and intoxication pathway(s), emphasizing the differences between the different family members and the characteristics that distinguish saporin from the catalytic subunit of the prototype Type II RIP ricin. The use of heterologous systems for the production of saporin and saporin-based chimeric toxins is also described.