PURIFICATION AND CHARACTERIZATION OF 3 MITOGENIC LECTINS FROM THE ROOTS OF POKEWEED (PHYTOLACCA-AMERICANA)

Three mitogenic lectins, designated PL-A, PL-B, and PL-C, were purifie d from the roots of pokeweed (Phytolacca americana) using Q-Sepharose column chromatography followed by gel filtration on Sephadex G-75, hyd rophobic chromatography on Butyl-Toyopearl, and FPLC on a Mono-Q colum n. PL-A, PL-B, and PL-C are acidic proteins having isoelectric points of 4.35 and their apparent molecular masses were 22, 48, and 21kDa by SDS-polyacrylamide gel electrophoresis in the presence of 2-mercaptoet hanol, respectively, The three lectins have similar amino acid composi tions rich in half-cystine and similar N-terminal sequences, indicatin g that they are homologous proteins, Identical sequences of N-terminal regions and six corresponding tryptic peptides in PL-A and PL-B sugge sted that PL-A may be an N-terminal half fragment of PL-B. Although al l of three lectins have mitogenic activities, PL-B is a mitogenic lect in with the most potent hemagglutinating and mitogenic activities, and PL-C has almost no hemagglutinating activity.