Isolation and Sequencing of a cDNA Clone Encoding Lysosomal Membrane Glycoprotein mLAMP-1: Sequence Similarity to Proteins Bearing Onco-Differentiation Antigens

摘要

We have isolated and sequenced a cDNA clone encoding the mouse mLAMP-1 major lysosomal membrane glycoprotein. The deduced protein sequence, which included the NH(2)-terminal portion of the mLAMP-1 molecule, consisted of 382 amino acids. The predicted structure of this protein included an NH(2)-terminal intralumenal domain consisting of two homology units of approximately 160 residues each, separated by a proline-rich hinge region. Each homology unit contained four cysteine residues, with two intercysteine intervals of 36 to 38 residues and one of 68 or 76 residues. The molecule also contained 20 Asn-linked glycosylation sites within residues 1 to 287, a membrane-spanning region from residues 347 to 370, and a carboxyl-terminal cytoplasmic domain of 12 residues. The biochemical properties and amino acid sequence of mLAMP-1 were highly similar to those of two other molecules that have been studied as cell surface onco-differentiation antigens: a highly sialylated, polylactosaminoglycan-containing glycoprotein isolated from human chronic myelogenous leukemia cells and the mouse gp130 (P2B) glycoprotein, in which an increase in Beta 1-6 branching of Asn-linked oligosaccharides has been correlated with metastatic potential in certain tumor cells. Keywords: Gene mapping. (kt)