1egg | pdb_00001egg
STRUCTURE OF A C-TYPE CARBOHYDRATE-RECOGNITION DOMAIN (CRD-4) FROM THE MACROPHAGE MANNOSE RECEPTOR
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Overview
The mannose receptor of macrophages and liver endothelium mediates clearance of pathogenic organisms and potentially harmful glycoconjugates. The extracellular portion of the receptor includes eight C-type carbohydrate recognition domains (CRDs), of which one, CRD-4, shows detectable binding to monosaccharide ligands. We have determined the crystal structure of CRD-4. Although the basic C-type lectin fold is preserved, a loop extends away from the core of the domain to form a domain-swapped dimer in the crystal. Of the two Ca(2+) sites, only the principal site known to mediate carbohydrate binding in other C-type lectins is occupied. This site is altered in a way that makes sugar binding impossible in the mode observed in other C-type lectins. The structure is likely to represent an endosomal form of the domain formed when Ca(2+) is lost from the auxiliary calcium site. The structure suggests a mechanism for endosomal ligand release in which the auxiliary calcium site serves as a pH sensor. Acid pH-induced removal of this Ca(2+) results in conformational rearrangements of the receptor, rendering it unable to bind carbohydrate ligands.
About this Structure
1EGG is a Single protein structure of sequence from Homo sapiens with CA as ligand. Full crystallographic information is available from OCA.
Reference
Structure of a C-type carbohydrate recognition domain from the macrophage mannose receptor., Feinberg H, Park-Snyder S, Kolatkar AR, Heise CT, Taylor ME, Weis WI, J Biol Chem. 2000 Jul 14;275(28):21539-48. PMID:10779515
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