Cell surface components of Leishmania: identification of a novel parasite lectin?

Protozoan parasites of the genus Leishmania have a glycoconjugatesurface coat (the glycocalyx) that acts as the interface betweenthe parasite and its external environment. The prinicipal componentsof the glycocalyx, the lipophosphoglycans and the glycoinositolphospholipids,have a variety of functions that facilitate parasite survivalin both the extracellular and the intracellular stages of thelife cycle. Recently, a novel hydrophilic Leishmania protein,the Gene B protein, has been identified on the surface of infectiveparasite stages. Attachment to the surface appears to be byassociation between a region of repeated amino acids in thismolecule and components of the glycocalyx. As a consequence,the Gene B protein is exposed on the parasite surface whileother peptides are buried beneath the glycocalyx. The putativefunctions of this unusual molecule are discussed. differentially regulated genes glycoconjugates infective parasites Leishmania surface protein     

Flow cytometry and surface plasmon resonance analyses demonstrate that the monoclonal antibody JIM19 interacts with a rice cell surface component involved in abscisic acid signalling in protoplasts.

Abscisic acid (ABA) is a plant hormone involved in many developmental and physiological processes, but as yet, no ABA receptor has been identified. Flow cytometry of rice protoplasts and immunoblotting of purified plasma membranes (PMs) have been used to demonstrate that the monoclonal antibody JIM19 recognizes carbohydrate epitopes of cell surface glycoproteins. Using surface plasmon resonance technology specific binding of PMs to JIM19 was observed. Such interaction was antagonized significantly by ABA, but not by the biologically inactive ABA catabolite phaseic acid. These in vitro interactions were correlated with the biological activities of JIM19, ABA and phaseic acid on activation of the ABA-inducible Em promoter using two different transient reporter gene assays, beta-glucuronidase/luciferase and quantitative flow cytometry of Aequoria green fluorescent protein. Pre-treatment with JIM19 resulted in significant inhibition of ABA-inducible gene expression. Taken together, these data suggest that JIM19 interacts with a functional PM complex involved in ABA signalling.