Type-2 Ribosome Inactivating Proteins from Mistletoe Plants: Gene Identification and Production of Active Recombinant Protein
Date Issued
2011
Date
2011
Author(s)
Lu, Tzu-Li
Abstract
Type-2 ribosome-inactivating proteins (RIP), composed of a toxic A-chain and lectin-like B-chain, display various biological functions, including cytotoxicity and immunomodulation. One of the most noticeable for their potential therapeutic uses might be mistletoe lectin I (ML-I), which was isolated from Viscum album and has been identified as the main active component of mistletoe extracts, a widely applied herbal medicine in Europe for complementary treatment of cancer patients. Interestingly, experiments in animal models suggest that ML-I-mediated inhibition of tumor growth is primarily associated with immunomodulatory efficacy. High-dose ML-I may fail because of its cytotoxicity. Although the B-chain binding activity was proved necessary for immunostimulating effects induced by ML-I, whether a B-chain fragment is an active immunomodulator still remains questionable. In Taiwan, there are dozens of various mistletoe plants, which have also been used for alternative medicine. In this dissertation, we reported identification of two new mistletoe type-2 RIP genes, articulatin and alniformosanin genes, from V. articulatum and V. alniformosanae, respectively. We showed certain diversity existing among these mistletoe type-2 RIP genes and suggested further collection or planting of these scarce mistletoe plants for isolation and characterization of novel mistletoe type-2 RIPs be warranted. We also cloned articulatin A- and B-chain (rATA and rATB) to produce large quantity of active recombinant proteins for potential practical use. We have developed a low ionic strength solution to stabilize the aggregation-prone rATB during storage, which was very critical to studies on rATB and other type-2 RIP B-chain. Finally, we in vitro demonstrated the ribosome-inactivating activity of rATA and immunostimulating potential of such nonglycosylated rATB, and discussed their possible biotechnological uses as a toxin or an immunomodulator without unwanted cytotoxicity.
Subjects
Viscum articulatum
articulatin
Viscum alniformosanae
alniformosanin
articulatin B-chain
immunomodulation
ribosome inactivating protein
SDGs
Type
thesis
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