Purification and characterization of a D-mannose specific lectin from the green marine alga, Bryopsis plumosa Jong Won Han, 1 Min Gui Jung, 2 Min Jung Kim, 2 Kang Sup Yoon, 1 Key Pyoung Lee 2 and Gwang Hoon Kim 1 * 1 Department of Biology, and 2 Department of Chemistry, Kongju National University, Kongju 314-701, Korea SUMMARY A D-mannose specific lectin was purified from the green marine alga, Bryopsis plumosa (Huds.) Ag. The lectin agglutinated horse and sheep erythrocytes. Matrix assisted laser desorption/ionization time of flight mass spectrometry, size exclusion chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two dimensional gel electrophoresis (2DE) results showed that the lectin was a monomer with molecular weight of 17 kDa and pI 7.3. The agglu- tinating activity was inhibited by D-mannose (1 mM), a-methyl-D-mannose (4 mM) and L-fucose (8 mM). D-glucose (125 mM) showed weak inhibition. The lectin did not need divalent cations for agglutinating activity. N-terminal amino acid sequence of the lectin was ana- lyzed. As the lectin was novel, we named it BPL-2 (Bryopsis plumosa lectin 2). Full cDNA sequence of BPL-2 was obtained using cDNA library. It was com- prised of 624 bp of open reading frame and 167 bp/ 57 bp of 3′/5′ untranslated regions as well as N-terminal signal peptide. No antimicrobial activity of BPL-2 was observed in four bacteria strains tested. Key words: Bryopsis plumosa, cDNA, D-mannose, green algae, hemagglutinin, lectin. INTRODUCTION Lectins have been reported from various organisms including animals, plants, bacteria, viruses and insects (Wong et al. 2008). Lectin is a protein that binds to glycoconjugates and precipitates them (Boyd & Shap- leigh 1954; Goldstein et al. 1980). Lectins were rede- fined as proteins possessing at least one non-catalytic domain that binds reversibly to a specific mono- or oligosaccharide. Plant lectins are subdivided into several groups; glucose/mannose specific, D-galactose/ N-acetyl-D-galactosamine (Gal/GalNAc) specific, N-acetyl-D-glucosamine (GlcNAc) specific, L-fucose specific and sialic acid specific lectins (Pusztai 1991). Carbohydrate binding ability of lectin is important in biological and medical study due to their involvement in signaling processes and non-immune defense system (Peumans & Van Damme 1995). Lectins were used as powerful tools in a glycobiology for the detection, isolation, and characterization of glycoconjugates (Shibuya et al. 1988a). Some of the lectin groups have properties such as anti-HIV virus, anti-inflammable, anti-microbial, anti-fungal, anti-tumor and mitogenic activities (Garred et al. 1997; Ngai & Ng 2007; Pohl- mann 2008; Wellman-Labadie et al. 2008). Mannose binding lectins are considered as biologi- cally important proteins since mannose and mannan are widely distributed in the cells and most of the mannose binding lectins can interact with cell surface glycocon- jugates (Ofek & Sharon 1988). Many mannose binding lectins showed anti-fungal and/or anti-microbial activi- ties (Ngai & Ng 2007). Moreover, mannose binding lectin could bind to the antibody, which made this lectin useful as a simple purification tool of antibodies (Shibuya et al. 1988b; Monzo et al. 2007). Algal lectins were related to cell–cell recognition, sexual reproduction, innate immune system, regenera- tion of cell and wound healing processes (Kim et al. 2001, 2006, 2007). In contrast to higher-plant lectin research, the study on algal lectins has progressed at a much slower pace because of the difficulties of isolat- ing and obtaining sufficient materials (Rogers & Hori 1993; Hori et al. 1996; Wang et al. 2004; Nagano et al. 2005). So far, few algal lectins have been char- acterized with molecular methodology (Hori et al. 2000) and information about the genetic coding of algal lectin is very scarce (Yoon et al. 2008). A GlcNAc and GalNAc specific lectin involved in protoplast regen- eration was isolated from Bryopsis plumosa (Kim et al. 2006), and its molecular characteristics were analyzed (Yoon et al. 2008). However, the presence of other types of lectins has also been predicted in B. plumosa (Kim et al. 2006). In the present study, we report the isolation of a new type of lectin in B. plumosa and characterized its molecular and biological properties. *To whom correspondence should be addressed. Email: ghkim@kongju.ac.kr Communicating editor: T. Motomura. Received 7 December 2008; accepted 2 November 2009. doi: 10.1111/j.1440-1835.2010.00572.x Phycological Research 2010; 58: 143–150 © 2010 Japanese Society of Phycology