Abstract
To date, a number of mannose-specific lectins have been isolated and characterized from seaweeds, especially from red algae. In fact, man-specific seaweed lectins consist of different structural scaffolds harboring a single or a few carbohydrate-binding sites which specifically recognize mannose-containing glycans. Depending on the structural scaffold, man-specific seaweed lectins belong to five distinct structurally-related lectin families, namely (1) the griffithsin lectin family (β-prism I scaffold); (2) the Oscillatoria agardhii agglutinin homolog (OAAH) lectin family (β-barrel scaffold); (3) the legume lectin-like lectin family (β-sandwich scaffold); (4) the Galanthus nivalis agglutinin (GNA)-like lectin family (β-prism II scaffold); and, (5) the MFP2-like lectin family (MFP2-like scaffold). Another algal lectin from Ulva pertusa, has been inferred to the methanol dehydrogenase related lectin family, because it displays a rather different GlcNAc-specificity. In spite of these structural discrepancies, all members from the five lectin families share a common ability to specifically recognize man-containing glycans and, especially, high-mannose type glycans. Because of their mannose-binding specificity, these lectins have been used as valuable tools for deciphering and characterizing the complex mannose-containing glycans from the glycocalyx covering both normal and transformed cells, and as diagnostic tools and therapeutic drugs that specifically recognize the altered high-mannose N-glycans occurring at the surface of various cancer cells. In addition to these anti-cancer properties, man-specific seaweed lectins have been widely used as potent human immunodeficiency virus (HIV-1)-inactivating proteins, due to their capacity to specifically interact with the envelope glycoprotein gp120 and prevent the virion infectivity of HIV-1 towards the host CD4+ T-lymphocyte cells in vitro.
Highlights
Lectins have been identified as sugar-binding proteins, in all groups of living organisms including plants, animals, fungi and bacteria, and even in viruses and mycoplasms
The present review presents an exhaustive overview on the structure-function relationships of man-specific lectins from seaweeds, in relation with their potential biomedical applications as anti-human immunodeficiency virus (HIV) and anticancer agents
Even though griffithsin is considered an efficient and safe anti-viral agent [63,68,76], the smaller 18-mer peptide derived from griffithsin, to the multivalent character of the griffithsin, which possesses three carbohydrate-binding sites (CBS) in each monomer of the dimeric structure, multiple interactions occurring between the lectin and the high-mannose glycans of gp120 favor the stability of the gp120-DC-SIGN complex and prevent the transmission of HIV to the CD4+ T-lymphocytes [54]
Summary
Lectins have been identified as sugar-binding proteins, in all groups of living organisms including plants, animals, fungi and bacteria, and even in viruses and mycoplasms. Other man-specific lectins belonging to different groups of algae including Rhodophyta (red algae), Pheophyceae (brown algae), Xanthophyceae (yellow-green algae), and Chlorophyta (green algae), have been identified and characterized, with respect to their anti-HIV properties [4,5]. In addition to their affinity for high-mannose glycans, both cloning and structural information have become available for a few seaweed lectins. The present review presents an exhaustive overview on the structure-function relationships of man-specific lectins from seaweeds, in relation with their potential biomedical applications as anti-HIV and anticancer agents
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