Collagen-like domain

Figure 13.3 A schematic summary of the galectins. (a) Galectins with one carbohydratebinding domain and (b) their noncovalent dimers, (c) Galectin-3 has a collagen-like domain and a carbohydrate-binding domain, (d) Galectins with two covalently hnked carbohydratebinding domains.

The collagen superfamily of proteins includes more than twenty colla gen types, as well as additional proteins that have collagen-like domains. The three polypeptide a-chains are held together by hydro gen bonds between the chains. Variations in the amino acid sequence of the a-chains result in structural components that are about the same size (approximately 1000 amino acids long), but with slightly dif ferent properties. These a-chains are combined to form the various types of collagen found in the tissues. For example, the most common collagen, type I, contains two chains called a1 and one chain called... 

The surfactant contains four unique proteins, designated SP-A, SP-B, SP-C, and SP-D.c e The major protein (SP-A) is a sialic acid-rich glycoprotein derived from a 26-kDa peptide, which contains a short collagen-like domain.eTk Like collagen, this domain contains glycosylated hydroxyproline. 

The unique Hyp residue may be important both at the molecular and higher-order structure levels in collagen. Bacteria and viruses lack prolyl hydroxylase and have no hydroxyproline in their collagen-like domains. The significant differences in their amino acid composition and sequence compared to animal collagens suggest the use of alternative stabilization strategies for the triple helix (Rasmussen et al., 2003). 

Wallis, R., Shaw, J. M., Uitdehaag, J., Chen, C. B., Torgersen, D., and Drickamer, K. (2004). Location of the serine protease-binding sites in the collagen-like domain of mannose-binding protein. J. Biol. Chem. 279, 14065—14073. 

Collagen is the major insoluble fibrous protein in the extracellular matrix and in connective tissue 80-90% of the collagen in the body consists of types 1, It and 111 (Table 12.2). The collagen superfamily consists of at least 20 collagen types, with as many as 38 distinct polypeptide chains and more than 15 additional proteins that have collagen-like domains. 

Clr 34-48 (6Ax 26,500) (6B X 26,500) (6C X 24,000) 83,000 collagen-like domains and petals , globular domains. Globular domains bind Fc regions of IgG and IgM antigen-antibody complexes, leading to activation of Clr and initiation of the classical pathway. Proenzyme to serine protease auto-activates and... 

Collagens are the most abundant proteins in the human body, constituting approximately 30% of its protein mass. At present, there are at least 28 known collagen types in vertebrates, containing a total of 42 distinct a-chains, and more than 20 additional proteins have collagen-like domains. Besides a-chains, there are also (3-chains (dimers of a-chains) and y-chains (trimers of a-chains). 

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