Cloning of the bovine 215-kDa cation-independent mannose 6-phosphate receptor

Four overlapping cDNA clones encoding a partial sequence of the cation-independent 215-kDa mannose 6-phosphate receptor have been identified by screening a fetal calf liver cDNA library with oligonucleotide probes. RNA hybridization analysis showed that the length of the mRNA is ~ 9.5 kilobases. Sequence analysis demonstrated that the clones consist of 4647 contiguous nucleotides and contain an open reading frame coding for a polypeptide of 1461 amino acids, which we estimate represents > 75% of the primary structure of the receptor. The deduced amino acid sequence indicates that the receptor has a carboxyl-terminal cytoplasmic domain of 163 amino acids that is rich in acidic residues, a 23-amino acid transmembrane segment, and an extracellular domain containing at least eight homologous repeats of ~ 145 amino acids. One of the repeats contains an additional 43-residue segment that is similar to the type II repeat of fibronectin. Each repeat contains a highly conserved 13-amino acid unit bordered by cysteine residues that may be functionally important.