The hydrophobic character of peanut (Arachis hypogaea) isoagglutinins

Peanut seed lectin (PNA) is widely used to identify tumor-specific antigens on the eukaryotic cell surface. In this work PNA was purified by affinity chromatography, using a column containing glutaraldehyde-treated human eryt hrocytes, whereas PNA isoforms were purified by hydrophobic interaction chr omatography using Phenyl-Sepharose. The affinity-purified PNA and its isofo rms consist of four equal subunits of 24.5 kDa each, all of which agglutina ted human sialidase-treated erythrocytes equally well; however, differences in their relative thermostabilities and sugar specificities for lactose we re observed. Fractions PNA-I and PNA-II possess higher affinity for lactose residues than the more hydrophobic isoforms III and IV. These findings sug gest that the differences observed in PNA isoagglutinins are due to hydroph obic regions of the protein that influence the three-dimensional organizati on of the molecule as well as its thermal stability and sugar specificity.