title: The N-terminal carbohydrate recognition site of the cation-independent mannose 6-phosphate receptor.
abstract: The 300-kDa cation-independent mannose 6-phosphate receptor (CI-MPR) plays a critical role in the trafficking of newly synthesized mannose 6-phosphate-containing acid hydrolases to the lysosome. The receptor contains two high affinity carbohydrate recognition sites within its 15-domain extracytoplasmic region, with essential residues for carbohydrate recognition located in domain 3 and domain 9. Previous studies have shown that these two sites are distinct with respect to carbohydrate specificity. In addition, expression of truncated forms of the CI-MPR demonstrated that domain 9 can be expressed as an isolated domain, retaining high affinity (Kd approximately 1 nm) carbohydrate binding, whereas expression of domain 3 alone resulted in a protein capable of only low affinity binding (Kd approximately 1 microm) toward a lysosomal enzyme. In the current report the crystal structure of the N-terminal 432 residues of the CI-MPR, encompassing domains 1-3, was solved in the presence of bound mannose 6-phosphate. The structure reveals the unique architecture of this carbohydrate binding pocket and provides insight into the ability of this site to recognize a variety of mannose-containing sugars.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Olson
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Dahms
authors.forename: Jung-Ja P
authors.initials: JJ
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D002417:Cattle; D003460:Crystallization; D015870:Gene Expression; D005966:Glucuronidase / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D008360:Mannosephosphates / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D017527:Receptor, IGF Type 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins
chemical_list: D008360:Mannosephosphates; D010446:Peptide Fragments; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; C027693:mannose-6-phosphate; D005966:Glucuronidase; D008358:Mannose