Isolation and sequencing of a cDNA clone encoding 107 kDa sialoglycoprotein in rat liver lysosomal membranes.

A cDNA for 107 kDa sialoglycoprotein (LGP 107), the major protein component of rat liver lysosomal membranes, was isolated and sequenced. The 1.8 kbp cDNA contained an open reading frame encoding a polypeptide consisting of 386 amino acid residues (Mr 41,914). The deduced NH2-terminal 10-residue sequence is identical with that determined for purified LGP 107. The primary structure deduced for LGP 107 contains 20 potential N-glycosylation sites and exhibits 82.5, 43 and 60% sequence similarities to mouse LAMP-1, chicken LEP 100, and a 120-kDa human lysosomal glycoprotein, respectively. Among these lysosomal glycoproteins, the amino acid sequence of the putative transmembrane segment is highly conserved. Northern blot hybridization analysis identified a single species of LGP 107 mRNA (2.1 kbp in length) in rat liver, kidney, brain, lung, spleen, heart and pancreas, although its level in pancreas was very low.