The crystal structure of a novel mammalian lectin, Ym1, suggests a saccharide binding site.
Ym1, a secretory protein synthesized by activated murine peritoneal macrophages, is a novel mammalian lectin with a binding specificity to GlcN. Lectins are responsible for carbohydrate recognition and for mediating cell-cell and cell-extracellular matrix interactions in microbes, plants, and animals. Glycosaminoglycan heparin/heparan sulfate binding ability was also detected in Ym1. We report here the three-dimensional structure of Ym1 at 2.5-A resolution by x-ray crystallography. The crystal structure of Ym1 consists of two globular domains, a beta/alpha triose-phosphate isomerase barrel domain and a small alpha + beta folding domain. A notable electron density of sugar is detected in the Ym1 crystal structure. The saccharide is located inside the triose-phosphate isomerase domain at the COOH terminal end of the beta-strands. Both hydrophilic and hydrophobic interactions are noted in the sugar-binding site in Ym1. Despite the fact that Ym1 is not a chitinase, structurally, Ym1 shares significant homology with chitinase A of Serratia marcescens. Ym1 and chitinase A have a similar carbohydrate binding cleft. This study provides new structure information, which will lead to better understanding of the biological significance of Ym1 and its putative gene members.
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan 115, Republic of China.
Y J
YJ
Sun
N C
NC
Chang
S I
SI
Hung
A C
AC
Chang
C C
CC
Chou
C D
CD
Hsiao
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry*; D002688:Chitinases / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D005916:Globulins / Q000737:chemistry; D005944:Glucosamine / Q000378:metabolism; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000502:physiology*; D008322:Mammals; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry; D014674:Plant Proteins, Dietary / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D001619:beta-N-Acetylhexosaminidases
D002241:Carbohydrates; D005916:Globulins; D037102:Lectins; D010940:Plant Proteins; D014674:Plant Proteins, Dietary; C066193:narbonin; C007110:concanavalin B protein, Canavalia ensiformis; D002688:Chitinases; C429541:Chil3 protein, mouse; D001619:beta-N-Acetylhexosaminidases; D005944:Glucosamine