Ricinus communis agglutinin (RCA120)

Ricinus communis agglutinin (RCA), specifically the RCA120 form, is a galactose-binding lectin isolated from the seeds of the castor bean plant (Ricinus communis) [UniProt, PubChem]. It is a member of the type II ribosome-inactivating protein (RIP) family and is structurally related to the highly toxic protein ricin, though RCA120 exists as a 120 kDa tetramer composed of two A-chains and two B-chains [NCBI, Wikipedia]. The B-chains are responsible for high-affinity binding to terminal galactose or N-acetylgalactosamine residues on the surface of eukaryotic cells, facilitating internalization via endocytosis [PubMed]. Once inside the cell, the A-chain functions as an N-glycosidase that depurinates the 28S ribosomal RNA, which irreversibly halts protein synthesis and induces cell death [UniProt]. While RCA is significantly less toxic than ricin due to its larger size and less efficient cytosolic translocation, it remains highly lethal and is used in laboratories to study cell-surface carbohydrates and neuronal pathways [NCBI]. In clinical research, it has been explored as a potential component of immunotoxins for targeted cancer therapy, where it is conjugated to antibodies to specifically eliminate tumor cells [PubMed].

Other names

RCA120Ricinus communis agglutinin IRCA-ICastor bean agglutininRicinus communis lectin

Binds to terminal galactose residues on cell surfaces via B-chains and inhibits protein synthesis by depurinating 28S ribosomal RNA via A-chains.