Abstract
We describe the isolation and sequencing of a cDNA encoding the mouse lysosomal membrane glycoprotein mLAMP-2 and the sequence differences that distinguish this molecule from the LAMP-1 class of proteins. An oligonucleotide probe corresponding to the NH2-terminal amino acid sequence of purified mLAMP-2 was synthesized by the polymerase chain reaction and used to screen several cDNA libraries. cDNA clones with an insert of 1,700 nucleotides were identified and sequenced. The deduced amino acid sequence of mLAMP-2 comprises a signal sequence of 25 residues and a 390-amino acid polypeptide (Mr 43,017) with the following putative domains: a large intraluminal region (residues 1-354) with 17 N-linked glycosylation sites (Asn-X-Ser/Thr), a hydrophobic transmembrane-spanning region of 24 residues (355-378), and a COOH-terminal cytoplasmic tail of 12 residues (379-390). When this sequence is compared with those of other lysosomal membrane glycoproteins, it is apparent that mouse LAMP-2 and human LAMP-2 form one homology class (LAMP-2) that is separated from the LAMP-1 class of proteins. The sequence differences in these two classes provide a basis for comparing the structure of the proteins with their biochemical and biological properties.
Highlights
EVIDENCE FOR TWO CLASSES OF LYSOSOMAL MEMBRANE GLYCOPROTEINS*Glycoproteins localized primarily to the limiting membrane of lysosomes of mouse (Chen et al, 1985a and 1985b), rat (Lewis et al, 1985; Barriocanal et al, 1986), chicken (Lippincott-Schwartz and Fambrough, 1986 and 1987), and human cells (Carlsson et al, 1988; Mane et al, 1989) have been identified recently by use of polyclonal and monoclonal antibodies
From the Department of Pharmacolofry Baltimore, h&yland 2j205 and J
When this sequence is compared with those of other lysosomal membrane glycoproteins, it is apparent that mouse LAMP-2 and human LAMP-2 form one homology class (LAMP-2) that is separated from the LAMP- 1 class of proteins
Summary
Glycoproteins localized primarily to the limiting membrane of lysosomes of mouse (Chen et al, 1985a and 1985b), rat (Lewis et al, 1985; Barriocanal et al, 1986), chicken (Lippincott-Schwartz and Fambrough, 1986 and 1987), and human cells (Carlsson et al, 1988; Mane et al, 1989) have been identified recently by use of polyclonal and monoclonal antibodies. These molecules appear to represent immunodominant components of the lysosomal membrane and have proved to be highly useful immunological markers in studies of lysosomal biogenesis and function, and in differentiating lysosomes from other organelles. CDNA of Mouse LAMP-2 two classes of proteins substantiate their distinct immunological identities and may have functional relevance
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