AMINO-ACID-SEQUENCE AND SOME PROPERTIES OF LECTIN-D FROM THE ROOTS OFPOKEWEED (PHYTOLACCA-AMERICANA)

Two pokeweed lectins, designated PL-D1 and PL-D2, have been isolated f rom the roots of pokeweed (Phytolacca americana) using chitin affinity column chromatography followed by gel filtration on a Sephacryl S-200 column and fast protein liquid chromatography on a Mono-Q column, and their amino acid sequences have been analyzed. PL-D1 consists of 84 a mino acid residues and has a molecular mass of 9317, while PL-D2 has a n identical sequence with PL-D1 except lack of the C-terminal Leu-Thr. PL-D is composed of two chitin-binding domains, A and B, with 50% hom ology with each other. Both PL-Ds did not agglutinate native rabbit er ythrocytes, but showed about 0.1% of the agglutinating activity of whe at germ agglutinin toward trypsin-treated erythrocytes. In the presenc e of beta(1-->4) linked oligomers of N-acetyl-D-glucosamine, which inh ibit the hemagglutination, PL-D1 had an ultraviolet-difference spectru m with maxima at 292-294 nm and 284-285 nm, attributed to the red shif t of the tryptophan residue, suggesting the location of tryptophan res idue(s) at or near saccharide-binding site of PL-D1.