A dimeric 62-kDa lectin exhibiting a novel N-terminal amino acid sequence was purified from caper (Capparis spinosa) seeds. The purification protocol involved anion-exchange chromatography, cation-exchange chromatography and, finally, gel filtration by FPLC on Superdex 75. Approx. 100-fold purification was achieved. The haemagglutinating activity of the lectin, which was stable in the pH range 1–12 and up to 40°C, could be inhibited by D(+) galactose, α-lactose, raffinose and rhamnose at 1 mM concentration, by 25 mM L(+)-arabinose and by 100 mM D(+)GlcN (glucosamine). The lectin potently inhibited HIV-1 reverse transcriptase with an IC50 of 0.28 μM and proliferation of both hepatoma HepG2 and breast cancer MCF-7 cells with an IC50 of approx. 2 μM. It induced apoptosis in HepG2 and MCF-7 cells. It manifested a weaker mitogenic activity on mouse splenocytes than ConA (concanavalin A). It inhibited mycelial growth in Valsa mali with an IC50 of 18 μM.

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