Mistletoe proteins

PROTEINS Asparaginase Bleomycin Mistletoe proteins Mitomalcin Neocarzinostatin Other plant proteins... 

Ribosome inactivating cytotoxic protein that irreversibly inhibits protein synthesis in cells, causing cell death. It is a solid obtained from the mistletoe plant (Viscum album). 

Pharmacotoxic and pharmacokinetic studies carried out for the new antitumor drug Aviscumine (rViscumin) were supported by a robust quantitative IPCR assay developed by Adler et al. [66, 85], The potency of this protein-based drug, derived from recombinant mistletoe lectine, required initial doses well below the quantification range accessible by conventional ELISA. An IPCR assay was adapted and validated for the quantification of rViscumin in standardized human serum [66, 85, 86] and subsequently... 

Chemical Abstracts Service Registry Number CAS 1393-62-0. Abrin is a toxalbumin similar in structure, absorption, and mechanism of action to ricin but is found not in castor beans but rather in jequirity beans. No reports of its use as a battlefield or terrorist agent exist, but in mice it is 75 times more potent than ricin. No specific treatment is available. Both ricin and abrin are type 2 ribosomal inhibitory proteins (RIPs) the other potent toxins in this class are Eranthis hyemalis lectin (EHL) from winter aconite, modeccin and volkensin from African succulents, and viscumin from mistletoe. 

Tonevitsky, A.G., Agapov, II, Pevzner, LB., Maluchenko, N.V., Moisenovich, M.M., Palmer, R.A., Yurkova, M., Pfuller, K. and Pfuller, U. (2004) A new gene encoding the ribosome-inactivating protein from mistletoe extracts. Arzneimittelforschung, 54, 242-249. 

ML-1. Lectin found in mistletoe. Comparable in toxicity with ricin and abrin inhibits protein synthesis as does ricin. 

Mimosa tenuiflora leaf extract Mistletoe (Viscum album) extract Mountain ash (Sorbus aucuparia) extract Mullein (Verbascum thapsus) extract Myrrh (Commiphora myrrha) extract Nettle (Urtica dioica) extract Oat (Avena sativa) protein Oleoresin capsicum Orris root extract Pansy (Viola tricolor) extract Parsley (Carum petroselinum) extract Passionflower (Passiflora incarnata) extract Periwinkle (Vinca minor) extract Quillaja (Quillaja saponaria) Rye (Secale cereale) extract... 

Known plant toxins are 1. the homologous viscotoxins (Af, 4,840 46 amino acid residues of known sequence 3 disulfide bridges) from leaves and branches of the European mistletoe, which have hypotensive activity and cause a slowing of the heart beat 2. the toxalbumins Ricin (see) and abrin, which inhibit protein biosynthesis. 

Mistletoe lectins have been extensively analyzed for their primary structure. Only the complete amino acid sequence of the A chain of mistletoe lectin 1 (VAA-1) has been determined thus far [25] but the data show a great homology with other ribosome inactivating proteins such as abrin a or ricin D with 111 and 103 amino acid residues conserved, respectively. 

Endo Y, Tsurugi K, Franz H (1988) The site of action of the A-chain of mistletoe lectin 1 on eukaryotic ribosomes the RNA N-glycosidase activity of the protein. FEBS Lett 231 378-380... 

Zinke H, Eck J, Langer M, Mockel B, Baur A, Lentzen H (1996) Molecular cloning of the Viscum album L. (mistletoe) gene for ML-1 and characterization of the recombinant protein. Phytomedicine 3 Suppl 1, 25... 

The tumour-inhibiting effects of extracts of the European mistletoe, Viscum album, have been found to be associated with the basic protein... 

Thus, the basic proteins of mistletoe can inhibit transcription just like the histones. Perhaps further investigation of this system will provide hints as to the mechanism of action of the histones. 

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