title: Amino acid sequence of the alpha subunit of human leukocyte adhesion receptor Mo1 (complement receptor type 3).
abstract: Mo1 (complement receptor type 3, CR3; CD11b/CD18) is an adhesion-promoting human leukocyte surface membrane heterodimer (alpha subunit 155 kD [CD11b] noncovalently linked to a beta subunit of 95 kD [CD18]). The complete amino acid sequence deduced from cDNA of the human alpha subunit is reported. The protein consists of 1,136 amino acids with a long amino-terminal extracytoplasmic domain, a 26-amino acid hydrophobic transmembrane segment, and a 19-carboxyl-terminal cytoplasmic domain. The extracytoplasmic region has three putative Ca2+-binding domains with good homology and one with weak homology to the "lock washer" Ca2+-binding consensus sequence. These metal-binding domains explain the divalent cation-dependent functions mediated by Mo1. The alpha subunit is highly homologous to the alpha subunit of leukocyte p150,95 and to a lesser extent, to the alpha subunit of other "integrin" receptors such as fibronectin, vitronectin, and platelet IIb/IIIa receptors in humans and position-specific antigen-2 (PS2) in Drosophila. Mo1 alpha, like p150, contains a unique 187-amino acid stretch NH2-terminal to the metal-binding domains. This region could be involved in some of the specific functions mediated by these leukocyte glycoproteins.
authors: Renal Unit, Children's Hospital, Boston, Massachusetts.
authors: M A
authors: MA
authors: Arnaout
authors: S K
authors: SK
authors: Gupta
authors: M W
authors: MW
authors: Pierce
authors: D G
authors: DG
authors: Tenen
mesh_terms: D000595:Amino Acid Sequence; D000954:Antigens, Surface / Q000235:genetics*; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics*; D015815:Cell Adhesion Molecules; D003001:Cloning, Molecular; D006801:Humans; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000235:genetics; D019030:Receptors, Vitronectin
chemical_list: D000954:Antigens, Surface; D001798:Blood Proteins; D015815:Cell Adhesion Molecules; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic; D019030:Receptors, Vitronectin