Purification and characterization of a new antiviral protein from the leaves of Pandanus amaryllifolius (Pandanaceae)

A lectin, designated Pandanin, was isolated from the saline extract of the leaves of Pandanus amaryllifolius, using ammonium sulfate precipitation, affinity chromatography on mannose-agarose and molecular size exclusion by gel filtration. Pandanin is an unglycosylated protein with a molecular mass of 8.0 kDa both after gel filtration and on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that it is a single polypeptide chain. The first 10 residues of the N-terminal amino acid sequence are DNILFSDSTL. An analysis of the sequence of first 30 amino acids at the N-terminal region shows that Pandanin has about 50-60% homology to those of mannose-specific lectins reported from monocot plants. Pandanin exhibits hemagglutinating activity toward rabbit erythrocytes, and its activity could be reversed exclusively by mannose and mannan. Pandanin also possesses antiviral activities against human viruses, herpes simplex virus type-1 (HSV-1) and influenza virus (H1N1) with 3 day's EC50 of 2.94 and 15.63 microM, respectively.