Molecular cloning of cDNAs encoding lamp A, a human lysosomal membrane glycoprotein with apparent Mr approximately equal to 120,000 - PubMed (original) (raw)

Comparative Study

Molecular cloning of cDNAs encoding lamp A, a human lysosomal membrane glycoprotein with apparent Mr approximately equal to 120,000

J Viitala et al. Proc Natl Acad Sci U S A. 1988 Jun.

Abstract

Although several lysosomal membrane glycoproteins have been characterized by using specific antibodies, none of the studies so far elucidated the amino acid sequence of a lysosomal membrane glycoprotein. Here we describe cDNA clones encoding for one of the lysosome-associated membrane proteins with apparent Mr approximately equal to 120,000, lamp A. The amino acid sequence based on the fully coded cDNA shows that as many as 18 potential N-glycosylation sites can be found in the total of 385 amino acid residues. The results obtained by endoglycosidase F digestion support the conclusion that this glycoprotein contains 18 N-glycans. These N-glycosylation sites are clustered in two domains; one contains 10 and the other contains 8 N-glycosylation sites. These domains are separated by a (proline-serine)-rich region that has a distinct homology to the IgA hinge structure. The first N-glycosylated domain is elongated to a potential leader peptide toward the NH2-terminal end. The second N-glycosylated domain, on the other hand, is connected to a putative transmembrane portion consisting of hydrophobic amino acids. This segment, in turn, is elongated to a short cytoplasmic segment composed of 11 amino acid residues at the COOH-terminal end.

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