Cloning and Expression of Mistletoe Lectin III B-Subunit

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I. B. Pevzner¹, I. I. Agapov¹, U. Pfueller², K. Pfueller², N. V. Maluchenko¹, M. M. Moisenovich¹, A. G. Tonevitsky^1*, and M. P. Kirpichnikov¹

¹Faculty of Biology, Lomonosov Moscow State University, 119899 Moscow, Russia; fax: (7-095) 196-0522; E-mail: tonevits@genetika.ru

²Institute of Phytochemistry, University of Witten/Herdecke, Stockumer Str. 10, D-58448, Witten, Germany; E-mail: uwep@uni-wh.de

^* To whom correspondence should be addressed.

Received March 3, 2004; Revision received April 5, 2004

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Aqueous extracts of mistletoe (Viscum album L.) contain toxic proteins (lectins) MLI (viscumin), MLII, and MLIII. We previously cloned the gene encoding MLIII precursor. In the present study, a gene fragment encoding the carbohydrate-binding subunit of mistletoe toxic lectin MLIII was cloned and expressed in Escherichia coli cells. The structure and immunochemical properties of recombinant MLIII B-subunit were investigated using a panel of monoclonal antibodies against ML-toxins. Sugar-binding activity of recombinant MLIII B-subunit was determined by ELISA. Amino acid sequence analysis of the cloned MLIII compared with known mistletoe toxins and other ribosome-inactivating type II proteins (ricin, abrin a, and nigrin b B-subunits) revealed essential features of the recombinant MLIIIB primary structure that could determine sugar specificity of the lectin as well as immunomodulating and anti-tumor properties of mistletoe extracts.

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KEY WORDS: mistletoe toxic lectin, recombinant MLIII B-subunit, monoclonal antibody

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