Structure of human stabilin-1 interacting chitinase-like protein (SI-CLP) reveals a saccharide-binding cleft with lower sugar-binding selectivity.Meng, G., Zhao, Y., Bai, X., Liu, Y., Green, T.J., Luo, M., Zheng, X.
(2010) J.Biol.Chem. 285: 39898-39904
- PubMed: 20724479
- DOI: 10.1074/jbc.M110.130781
- PubMed Abstract:
Human secreted protein stabilin-1 interacting chitinase-like protein (SI-CLP) has been identified as a novel member of Glyco_18 domain-containing proteins that is involved in host defense and inflammatory reactions. Efficient secretion of SI-CLP is m ...
Human secreted protein stabilin-1 interacting chitinase-like protein (SI-CLP) has been identified as a novel member of Glyco_18 domain-containing proteins that is involved in host defense and inflammatory reactions. Efficient secretion of SI-CLP is mediated by its interaction with the endocytic/sorting receptor stabilin-1. SI-CLP is expressed abundantly in macrophages and neutrophils and is up-regulated by Th2 cytokine IL-4 and glucocorticoid, which suggest that SI-CLP could be a marker for adverse effects of glucocorticoid therapy. To gain insight into the biological function of SI-CLP, we determined the crystal structure of SI-CLP at 2.7 Å resolution by x-ray crystallography and found that it featured a typical triose-phosphate isomerase barrel fold with a putative saccharide-binding cleft. Comparison with other chitinase-like proteins showed the cleft to be atypically wide and open. The saccharide-binding capacity of SI-CLP was investigated, and its ligand-binding specificity was found to relate to the length of the oligosaccharides, with preference for chitotetraose. Further investigations reveal that SI-CLP could bind LPS in vitro and neutralize its endotoxin effect on macrophages. Our results demonstrate the saccharide-binding property of SI-CLP by structure and in vitro biochemical analyses and suggest the possible roles of SI-CLP in pathogen sensing and endotoxin neutralization.
National Laboratory of Protein Engineering and Plant Genetic Engineering, Department of Biochemistry and Molecular Biology, College of Life Sciences, Peking University, Beijing 100871, China