We previously isolated a lectin of the Korean mistletoe (Viscum album coloratum) [Yoon et al. (1999)]. The cDNA clones that encode the A- or the B-chain of the Korean mistletoe lectin were cloned by reverse tran-scriptase polymerase chain reaction (RT-PCR). The mRNAs that were extracted from the Korean mistletoe were amplified, ligated into the pGEM-T easy vector, and screened with a Korean mistletoe lectin-specific probe. The probe was prepared by PCR amplification of the Korean mistletoe DNA using a primer set de-signed on the basis of amino acid sequences of the Ko-rean mistletoe lectin that we had purified and reported. Unlike a recent report, which states that the Euro-pean mistletoe lectin gene has no isoforms, several dif-ferent clones of the A- and B-chains of the Korean mistletoe lectin were cloned from the same primer set. Three clones of each were selected for sequencing. The sizes of the A-chains were 762, 762, and 768 bp, re-spectively. The B-chain sizes were 798, 789, and 789 bp, respectively. Each of the clones showed significant variation in the amino acids sequence, including the N-linked glycosylation sites of the lectin. The sequence analysis of each of the Korean lectin clones, in com-parison with the European mistletoe lectin and the other type II ribosome binding proteins, is discussed in the text. In addition, Southern blot analysis of the Ko-rean mistletoe genomic DNA, restricted by different enzymes and hybridized with the lectin DNA, showed multi-bands, supporting the existence of multicopy genes or a gene family. These data suggest that heterogeneity of the mistle-toe lectin is not only introduced by post-translational lectin genes.

Keywords: Lecti, Isotype, Isolectin, Isoforms, cDNA, Cloning