CD 69 antigen of human lymphocytes is a calcium-dependent carbohydrate-binding protein

CD69 is a signal transducing molecule of hematopoietic cells. Previous molecular cloning of CD69 has revealed a type II transmembrane orientation and the presence of an extracellular domain related to the Ca(2+)-dependent (C-type) animal lectins. As the predicted amino acid sequence for the lectin-like domain is highly divergent from those of other C-type lectin-like proteins - a feature shared with NKR-P1 of natural killer cells - CD69 and NKR-P1 are among proteins assigned to a separate group, group V. To initiate ligand identification studies, we have prepared soluble forms of CD69 protein by bacterial expression of its extracellular portion. We show that cysteine 68 located in the short membrane-proximal neck region of CD69 which adjoins the C-terminal lectin-like domain is a critical element for dimerization. We have evidence that the soluble dimeric CD69 has a tight association with calcium, a feature shared with NKR-P1, and that it is a carbohydrate-binding protein with N-acetyl-D-glucosamine and N-acetyl-D-galactosamine as the best inhibitors: 4-8 x 10(-5) M giving 50% inhibition of binding to N-acetyl-D-glucosamine neoglycoprotein. Thus, the tight association with calcium and high affinities for carbohydrate binding appear to be features of at least two members of the C-type lectin group

Metal uptake and nanoparticle synthesis in hairy root cultures

Hairy roots are a convenient experimental tool for investigating the interactions between plant cells and metal ions. Hairy roots of species capable of hyperaccumulating Cd and Ni have been applied to investigate heavy metal tolerance in plants; hairy roots of nonhyperaccumulator species have also been employed in metal uptake studies. Furnace treatment of hairy root biomass containing high concentrations of Ni has been used to generate Ni-rich bio-ore suitable for metal recovery in phytomining applications. Hairy roots also have potential for biological synthesis of quantum dot nanocrystals. As plant cells intrinsically provide the confined spaces needed to limit the size of nanocrystals, hairy roots cultured in bioreactors under controlled conditions are a promising vehicle for the manufacture of peptide-capped semiconductor quantum dots

Plant products with antifungal activity. From field to biotechnology strategies

In this chapter, informations on the recent advances regarding antifungal activity of natural products obtained from plants collected directly from their natural habitat or from plant cell and organ, cultures have been reported. The biotechnological approaches could increase uniformity and predictability of the extracts and overcome problems associated with geographical, seasonal, and environmental variations. Human fungal pathogens are the cause of severe diseases associated with high morbidity and mortality. The major human fungal pathogens are Candida species, dermatophytes, Aspergillus species, and Cryptococcus neoformans. Side effects and resistance are frequently attributed to the current antifungal agents. Moreover, the treatments often require long-term therapy and are not resolving. Plants represent a source of antifungal agents, but up to date, the number of new phytochemicals reaching the market is very low. This review attempts to summarize the current status of botanical screening efforts, as well as in vitro and in vivo studies on antifungal activity of plant products. Despite the currently non-uniform regulatory framework in all the states, the plant-derived products are increasingly in demand for their effectiveness. The basic conclusion from these studies is that rigorous, well-designed clinical trials are needed to validate the effectiveness and safety of plant extracts for their use as antifungals