Ribosome-inactivating proteins RIP

Type II ribosome-inactivating protein (RIP)/ polynucleotide aminoglycosidase (PAG) 9.IB... 

Ricin is a lectin-type globular glycoprotein and consists of A and B chains (Doan, 2004 Li and Pestka, 2008). Ricin is considered a Type 2 ribosome-inactivating protein (RIP) (Millard and LeClaire, 2008). The ricin B chain attaches to the plasma membrane at the galactose receptors, pits are... 

Various plant toxins, mostly ribosome-inactivating proteins (RIPs), have been identified that bind to any mammalian cell surface expressing galactose units and are subsequently internalized by RME (67). Toxins such as nigrin b (68), a-sarcin (69), ricin and saporin (70), viscumin (71), and modeccin (72) are highly toxic upon oral administration (i.e., are rapidly internalized). The possibility exists, therefore, that modified and, most important, less toxic subunits of these compound can be used to facilitate the uptake of macro-molecular compounds or microparticulates. 

Kojima et al. [46] have isolated a protein from the leaves of Artemisia princeps by means of ultrafiltration and Sephadex chromatography. This protein has a molecular weight of 500,000-1000,000 Da and induces interferon when administered orally and parenterally. In recent years the ribosome inactivating proteins (RIPs) have gained particular interest due to their multiple effects on HIV-infections. Whereas... 

Many molds and plants produce toxins, which are protective reagents, termed ribosome-inactivating proteins (RIPs), directed at particular cells and their ribosomes. These toxins are classified as either type I or type II RIPs according to the number of polypeptide chains. 

Fig. 1. Schematic representation of the structure of different types of ribosome-inactivating proteins (RIPs). Type 1 RIPs consist of one or two smaller polypeptide chains, held together by noncovalent interactions, featuring N-glycosidase activity. Type 3 RIPs consist of a polypeptide chain harboring N-glycosidase activity and a second domain of unknown function. Both types belong to the superfamily of holo-RIPs. Type 2 RIPs are representatives of chimero-RIPs consisting of two structurally unrelated polyjseptide chains linked by a disulfide bridge.

Ribosome-inactivating proteins (RIPs) are toxins that act intracellularly. They consist of two different subunits a subxmit A that is responsible for the enzymatic activity of the toxin and a subunit B that binds to a specific receptor on the host cell membrane, thus allowing the A subxmit. 

The seeds of the ubiquitous castor bean plant (Ricinus communis) contain high concentrations of a highly toxic, relatively stable, heterodimeric, glycoprotein toxin called ricin, which is a type 2 ribosome-inactivating protein (RIP) (Burrows and Tyrl, 2001 Millard and LeClaire, 2008 Salem et al., 2008b). The inhibition of protein synthesis by ricin and related t5q>e 2 RIPs has been associated with endothelial toxicity and, depending on the route of exposure, severe gastrointestinal or respiratory... 

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