Lectin tutorial Jawahar Swaminathan

Lectins

Lectins are carbohydrate recognition proteins, found in almost all species. They play an important role in cell-cell recognition, cell communication, transport of various molecules, such as sugars, and in the immune system. Lectins are classified according to their structure and the nature of the carbohydrate that they bind (see, for example, the classification of animal lectins).

The sugar binding function of lectins can be attributed to a domain within the larger protein, which is called the Carbohydrate Recognition Domain (CRD). It is structure and organization of the CRD region that distinguishes different types of lectin.

We will be looking here at a particular family of lectins, the C-type lectins. This group is so named because they bind sugars in a calcium-dependent manner. Before they are able to bind sugars, this group of lectins must first bind calcium, which stabilises the conformation of the sugar binding site.

C-type lectins predominantly recognize mannose (PDB three-letter code MAN, for alpha-D-mannose). The representative structure in this family is that of the mannose-binding protein (PDB entry 1RTM). The role of the molecule is to bind to the sugar-coated cell walls of gram-positive bacteria, as one of the first immune system responses to an invasion. The molecules exist in multimeric complexes, enhancing their ability to opsonize invading bacteria. This protein is therefore a member of the innate immune system.

This tutorial will show you some of the ways that we can analyse the members of this family of proteins using some of the tools that are available at the MSD.