Lectin c-type

C-type lectins Characterized by a Ca +-dependent carbohydrate recognition domain (CRD) includes the mammalian asialoglycoprotein receptor, the selectins, and the mannosebinding protein... 

Figure 47-10. Schematic diagram of the structure of human L-selectin. The extracellular portion contains an amino terminal domain homologous to C-type lectins and an adjacent epidermal growth factor-like domain. These are followed by a variable number of complement regulatory-like modules (numbered circles) and a transmembrane sequence (blackdiamond). A short cytoplasmic sequence (open rectangle) is at the carboxyl terminal. The structures of P- and E-selectin are similar to that shown except that they contain more complement-regulatory modules.The numbers of amino acids in L-, P-, and E- selectins, as deduced from the cDNA sequences, are 385,789, and 589, respectively. (Reproduced, with permission, from Bevilacqua MP, Nelson RM Selectins. J Clin Invest 1993 91 370.)...

Several other C-type lectins have since been found in Toxocara (Fig. 12.4). Two are simple variants of TES-32, differing by 13-17% in amino acid sequence but with identical ligand binding sites these have been termed CTL-2 and CTL-3. It has yet to be determined whether these additional lectins are alleles or represent different coding loci, and it has not been established whether they are also secreted. A fourth lectin, CTL-4, corresponds to TES-70 (Loukas et al, 2000), as described below. In addition, there is some evidence that TES-45 and TES-55 are lectins, as detailed below. 

CTL-1 Cys-rich domain Thr- tract " W C-Type Lectin Domain ... 

Fig. 12.4. Schematic summary of the four T. canis C-type lectins discovered.

Loukas, A. and Maizels, R.M. (1999) Helminth C-type lectins and host-parasite interactions. Parasitology Today 16, 333-339. 

Loukas, A.C., Doedens, A., Hintz, M. and Maizels, R.M. (2000) Identification of a new C-type lectin, TES-70, secreted by infective larvae of Toxocara canis, which binds to host endothelial cells. Parasitology (in press). 

There are three types of selectins responsible for the attachment of leukocytes to the endothelium, as shown in Table 3.1. Selectins possess three types of domains a C-type lectin domain, an epidermal growth-factor-like domain and between two and nine regulatory domains. 

CLECT C-type lectin (CTL) or carbohydrate-recognition domain (CRD) E(M) 0(0) 246(314) 1B6E... 

The C-terminal domain is a Ca2+-dependent C-type lectin (Chapter 4), while the N-terminal domain is involved in oligomer formation through disulfide bridges. The overall structure is similar to that of the complement protein Clq (Chapter 31).e) Protein D is also collagen-like1 but evidently plays a very different functional role than SP-A. The latter associates with the major surfactant lipids but SP-D does not. It does bind phosphatidyl inositol" and gluco-sylceramide, lipids that are present in small amounts. Perhaps SP-D helps to remove these polar lipids which might interfere with surfactant action.6 Both proteins A and D may also have functions in the immune system.1... 

Fig. B.5.2. Crystal structure of an a-D-mannose unit bound to the C-type lectin rat mannose-binding protein A (MBP-A,...

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