University Publications

Lectins are defined as the carbohydrate-binding proteins of non-immune origin that can interact and precipitates glycoconjugates from their solutions. Due to these features, many applications have been discovered for these proteins. The present investigation has been devoted to optimising a protocol for the extraction, purification and characterization of a lectin from the seeds of the medicinal plant Ocimum basilicum (OBSL). Different extraction procedures were employed, including varying buffers with variable pHs. Precipitation of the seeds' crude protein extract with salting-out using solid ammonium sulphate (AmS) at 40, 60 and 80% concentrations resulted in the segregation of the lectins into at least three isoforms. The lectin was purified to apparent electrophoretic homogeneity by fetuin-agarose affinity resin. The lectin was a trimer composed of three subunits of different molecular weights. Scanning the three AmS precipitated protein fractions at the UV ranges, indicates that the protein is rich in tryptophan rather than tyrosine. The lectin haemagglutination pattern studies showed that OBSL had a better affinity for the B+ human blood group, sheep and rabbit erythrocytes as compared to other human and animal blood types. The lectin was not inhibited by any simple sugar indicating its classification as a lectin with complex sugar specificity. OBSL was stable within the pH range from 2.5 to 10.5 showing two pH activity optima. It was optimally active from 40 to 50 °C. This study represents the first-ever report on this plant lectin and might stimulate further studies to extensively characterize this protein. *Corresponding author: ehkonozy@yahoo.com; ehkonozy@act.gov.sa