A new isolation procedure and further characterisation of the lectin from the red marine alga Ptilota serrata

Ptilota serrata has been shown previously to contain a lectin (PSL) which is non-specific for human blood groups. We report here a new isolation procedure for PSL using a single step affinity chromatography technique on cross-linked guar gum and further characterisation studies. PSL was inhibited by galactose and its derivatives. The carbohydrates o-nitrophenyl-N-acetyl-alpha-D-galactoside, p-nitrophenyl-N-acetyl-B-D-galactoside and lactose were strong inhibitors. The glycoproteins porcine stomach mucin, asialo bovine mucin and asialofetuin were also inhibitory. The Mr of PSL, determined by gel filtration, was 55,470. SDS-PAGE revealed one single protein band with Mr of 18,390, indicating the native protein to be a trimer of apparently identical subunits. PSL was shown to contain large amounts of acidic and hydroxyl amino acids but low in basic amino acids.