The anti-human immunodeficiency virus (HIV) I/II activity of a
mannose and
sialic acid binding
lectin isolated from rhizomes of Polygonatum cyrtonema Hua was elucidated by comparing its
HIV infection inhibitory activity in MT-4 and CEM cells with that of other
mannose-binding lectins (MBLs). The anti-HIV activity of Polygonatum cyrtonema Hua
lectin (PCL) was 10- to 100-fold more potent than other tested MBLs, but without significant cytotoxicity towards MT-4 or CEM cells. To amplify
cDNA of PCL by 3'/5'-rapid amplification of
cDNA ends (RACE), the 30
amino acids of N-terminal were determined by sequencing and the degenerate
oligonucleotide primers were designed. The full-length
cDNA of PCL contained 693 bp with an open reading frame encoding a precursor
protein of 160
amino acid residues, consisting of a 28-residue
signal peptide, a 22-residue C-terminal cleavage
peptide and a 110-residue mature
polypeptide which contained three tandemly arranged subdomains with an obvious sequence homology to the monocot MBL. However, only one active
mannose-binding site (QDNVY) was found in subdomain I of PCL, that of subdomain II and III changed to HNNVY and PDNVY, respectively. There was no intron in PCL, which was in good agreement with other monocot MBLs. Molecular modeling of PCL indicated that its three-dimensional structure resembles that of the snowdrop
agglutinin. By docking, an active
sialic acid-binding site was found in PCL. The instabilization of translation initiation region (TIR) in
mRNA of PCL benefits its high expression in rhizomes.