Recent progress in glycobiology has revealed that cell surface oligosaccharides play an essential role in recognition events. More precisely, these saccharides may be complexed by lectins, carbohydrate-binding proteins other than enzymes and antibodies, able to recognise sugars in a highly specific manner. The ubiquity of lectin–carbohydrate interactions opens enormous potential for their exploitation in medicine. Therefore, extraordinary effort is made into the identification of new lectins as well as into the achievement of a deep understanding of their functions and of the precise mechanism of their association with specific ligands. In this review, a summary of the main features of lectins, particularly those found in legumes, will be presented with a focus on the mechanism of carbohydrate-binding. An overview of lectin–carbohydrate interactions will also be given, together with an insight into their energetics. In addition, therapeutic applications of lectins will be discussed.

/pdf/lectins-tools-for-the-molecular-understanding-of-the-1ti7aeto54.pdf

Lectins: tools for the molecular understanding of the glycocode

Thermodynamic studies of lectin-carbohydrate interactions by isothermal titration calorimetry.

The central dogma of molecular biology limits the downstream flow of genetic information to proteins. Progress from the last two decades of research on cellular glycoconjugates justifies adding the enzymatic production of glycan antennae with information-bearing determinants to this famous and basic pathway. An impressive variety of regulatory processes including cell growth and apoptosis, folding and routing of glycoproteins and cell adhesion/migration have been unravelled and found to be mediated or modulated by specific protein (lectin)-carbohydrate interactions. The conclusion has emerged that it would have meant missing manifold opportunities not to recruit the sugar code to cellular information transfer. Currently, the potential for medical applications in anti-adhesion therapy or drug targeting is one of the major driving forces fuelling progress in glycosciences. In histochemistry, this concept has prompted the introduction of carrier-immobilized carbohydrate ligands (neoglycoconjugates) to visualize the cells' capacity to be engaged in oligosaccharide recognition. After their isolation these tissue lectins will be tested for ligand analysis. Since fine specificities of different lectins can differ despite identical monosaccharide binding, the tissue lectins will eventually replace plant agglutinins to move from glycan profiling and localization to functional considerations. Namely, these two marker types, i.e. neoglycoconjugates and tissue lectins, track down accessible binding sites with relevance for involvement in interactions in situ. The documented interplay of synthetic organic chemistry and biochemistry with cyto- and histochemistry nourishes the optimism that the application of this set of innovative custom-prepared tools will provide important insights into the ways in which glycans can act as hardware in transmitting information during normal tissue development and pathological situations.

Glycohistochemistry: the why and how of detection and localization of endogenous lectins.

Plants are regarded as a promising system for the production of heterologous proteins. However, little is known about the influence of plant development and growth conditions on N-linked glycosylation. To investigate this, transgenic tobacco (Nicotiana tabacum cv Samsun NN) plants expressing a mouse immunoglobulin G antibody (MGR48) were grown in climate rooms under four different climate conditions, i.e. at 15 degrees C and 25 degrees C and at either low or high light conditions. N-glycans on plantibodies and soluble endogenous proteins were analyzed with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS). Antibodies isolated from young leaves have a relatively high amount of high- mannose glycans compared with antibodies from older leaves, which contain more terminal N-acetylglucosamine. Senescence was shown to affect the glycosylation profile of endogenous proteins. The relative amount of N-glycans without terminal N-acetylglucosamine increased with leaf age. Major differences were observed between glycan structures on endogenous proteins versus those on antibodies, probably to be attributed to their subcellular localization. The relatively high percentage of antibody N-glycan lacking both xylose and fucose is interesting.

Influence of growth conditions and developmental stage on N-glycan heterogeneity of transgenic immunoglobulin G and endogenous proteins in tobacco leaves

A bunch of keys, one lock: The multivalent effect in glycosidase inhibition is a new, rapidly emerging area with exciting potential and scope. This review presents a description of the different types of neoglycoclusters and their evaluation as glycosidase inhibitors. The first promising therapeutic applications are discussed, as well as the mechanisms underlying the observed inhibitory multivalent effect.

The multivalent effect in glycosidase inhibition: a new, rapidly emerging topic in glycoscience.

Diocleinae Lectins Are a Group of Proteins with Conserved Binding Sites for the Core Trimannoside of Asparagine-linked Oligosaccharides and Differential Specificities for Complex Carbohydrates*

Flavia A.M. de Sousa

Papers

Diocleinae Lectins Are a Group of Proteins with Conserved Binding Sites for the Core Trimannoside of Asparagine-linked Oligosaccharides and Differential Specificities for Complex Carbohydrates*

Purification and characterization of a lectin from seeds of Vatairea macrocarpa duke

Thermodynamic binding studies of lectins from the diocleinae subtribe to deoxy analogs of the core trimannoside of asparagine-linked oligosaccharides.