Cloning and characterization of a human Mac-2-binding protein, a new member of the superfamily defined by the macrophage scavenger receptor cysteine-rich domain.
We have purified and sequenced a secreted glycoprotein from both the human breast carcinoma cell line, SK-BR-3, and human breast milk. The native protein binds specifically to a human macrophage-associated lectin known as Mac-2. This Mac-2 binding protein (Mac-2-BP) has an apparent native molecular mass of several million daltons and contains subunits of 85-97 kDa that are very susceptible to proteolysis at a dibasic cleavage site. Western analysis suggests that Mac-2-BP is found in serum, semen, saliva, urine, and tears, in addition to breast milk. The gene encoding Mac-2-BP was cloned from a cDNA bank of a human monocytic cell line, using degenerate PCR primers based on the protein sequence. Recombinant Mac-2-BP was expressed in Cos cells and secreted as a high molecular weight complex. The cDNA clone encodes a mature protein of 567 amino acids, preceded by an 18-amino acid leader. The mature protein contains 16 cysteines and has seven potential N-linked glycosylation sites. The first 106 amino acids represent a domain that is highly similar to an ancient protein superfamily defined by the macrophage scavenger receptor cysteine-rich domain.
Department of Biological Therapeutics Research, Chiron Corporation, Emeryville, California 94608.
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Koths
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Taylor
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Halenbeck
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Casipit
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Wang
D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm; D001483:Base Sequence; D014408:Biomarkers, Tumor; D001943:Breast Neoplasms; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification; D002460:Cell Line; D003001:Cloning, Molecular / Q000379:methods; D003545:Cysteine; D004247:DNA; D005260:Female; D015723:Gene Library; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008895:Milk, Human / Q000378:metabolism; D008969:Molecular Sequence Data; D009000:Monocytes; D005810:Multigene Family; D009838:Oligodeoxyribonucleotides; D011956:Receptors, Cell Surface / Q000235:genetics*; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014407:Tumor Cells, Cultured; D016326:Extracellular Matrix Proteins
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D003545:Cysteine; D004247:DNA; D006023:Glycoproteins; D009838:Oligodeoxyribonucleotides; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D011994:Recombinant Proteins; C081856:LGALS3BP protein, human; D016326:Extracellular Matrix Proteins