Affinity purified Pisum sativum lectin or agglutinin (PSA) is a heterodimer that consists of four subunits. It has a carbohydrate specificity towards α-linked mannose-containing oligosaccharides. It’s hemagglutinating activity can be inhibited by glucose, mannose, and sucrose. It does not have a blood group specificity. The N-terminal sequence of the lectin has shown some degree of homology compared to lectins from other legume species. Pisum sativum lectin has also shown mitogenic effect toward murine splenocytes and could inhibit activity of HIV-1 reverse transcriptase. PSA is often used to differentiate virally transformed from normal cells. Calcium and manganese ions are required for activity.
Cy5, when bound to Pisum sativum Lectin (PSA/PSL), can show the binding pattern of this lectin in cellular imaging and flow cytometry. The excitation wavelength required for Cy5 to fluoresce is high enough to avoid overlap with most other fluorochromes, making it useful for dual-labeling experiments. Because of this high excitation, there is typically less background from autofluorescence of biological specimens.