title: Cloning, primary structure and properties of a novel human integrin beta subunit.
abstract: The originally described integrin beta subunits that define the three subfamilies of integrin heterodimers are beta 1, beta 2 and beta 3. In this paper, we describe the isolation of a cDNA coding for a novel human integrin beta subunit, designated as beta 5. The beta 5 cDNA was isolated from a human thymic epithelial cell library, using oligonucleotide probes that were designed from a region highly conserved among the known beta 1, beta 2 and beta 3 sequences. The beta 5 cDNA codes for 799 (or 796) amino acids, including a 23 amino acid leader sequence. There are 776 (or 773) amino acids in the mature protein, which includes a long extracellular domain of 696 amino acids, a transmembrane domain and an intracellular C-terminal domain of 57 amino acids. The beta 5 sequence resembled the known beta 3, beta 1 and beta 2 sequences by 55, 43 and 38%, respectively, including conservation of 56/56 cysteines. Rabbit antiserum was prepared against a 20 amino acid synthetic peptide predicted from the beta 5 C-terminal sequence. This serum immunoprecipitated a beta 5 protein that was 100,000 Mr (reduced) and 95,000 Mr (nonreduced). Only a single alpha subunit was detected in association with beta 5, and that alpha subunit was immunochemically indistinguishable from the alpha v subunit previously found as part of the vitronectin receptor complex. By immunoprecipitation, beta 5 was most prevalent on carcinoma cell lines, was also present on hepatoma and fibroblast cell lines, and was absent from lymphoblastoid cells and platelets.
authors.affiliation: Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115.
authors.forename: H
authors.initials: H
authors.lastname: Ramaswamy
authors.forename: M E
authors.initials: ME
authors.lastname: Hemler
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D015342:DNA Probes; D014644:Genetic Variation; D006801:Humans; D016023:Integrins / Q000235:genetics*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010446:Peptide Fragments / Q000235:genetics; D011233:Precipitin Tests; D012689:Sequence Homology, Nucleic Acid
chemical_list: D015342:DNA Probes; D016023:Integrins; D046911:Macromolecular Substances; D010446:Peptide Fragments