| Description | The cation dependent mannose-6-phosphate (man-6-P) receptor is one of two transmembrane proteins involved in the transport of lysosomal enzymes from the Golgi complex and the cell surface to lysosomes [ ]. Lysosomal enzymes bearing phosphomannosyl residues bind specifically to man-6-P receptors in the Golgi apparatus and the resulting receptor-ligand complex is transported to an acidic prelyosomal compartment, where the low pH mediates dissociation of the complex. Binding is optimal in the presence of divalent cations.The amino acid sequence is a single polypeptide chain that contains a putative signal sequence and a transmembrane domain [ ]. The cation-dependent mannose 6-phosphate (M6P) receptor (CD-MPR) is present predominantly as a stable homodimer in membranes and has a single M6P-binding site per polypeptide [, ]. The molecule crystallizes as a homodimer with approximately 20% of the entire surface area of each monomer having contact with another through predominantly hydrophobic interactions []. Each monomer contains a single α-helix near its amino terminus followed by nine primarily anti-parallel β-strands that form two β-sheets, which are positioned orthogonally to each other. Extensive hydrophobic interactions are formed between the two β-sheets, which results in each monomer forming a flattened β-barrel structure. Six cysteine residues form three intramolecular disulphide bonds that are essential for the ligand-binding conformation of the receptor to be generated. The structures of the liganded molecules show that the carbohydrate-recognition domain of the enzyme lies relatively deep inside the protein, so that the terminal M6P residue and the penultimate sugar ring of bound pentamannosyl phosphate are mostly buried in the receptor. This deep binding pocket facilitates the formation of numerous interactions between the CD-MPR and its carbohydrate ligands. | Name | Cation-dependent mannose-6-phosphate receptor |
| Short Name | Man-6-P_rcpt_cation_dep | Type | Family |
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