277 zyxwvutsr Gene, 141 (1994) 277-281 0 1994 Elsevier Science B.V. All rights reserved. 037%1119/94/$07.00 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA GENE 07753 Bovine conglutinin (BC) mRNA expressed in liver: cloning and characterization of the BC cDNA reveals strong homology to surfactant protein-D (Recombinant DNA; influenza virus inhibitor; C-type lectin; collectins; opsonin; infection defense; HIV-l) Louis S. Lieu”, Rajeswari Sastry”, Kevan L. Hartshorna, Young Moo Leeb, Thomas B. Okarmab, Alfred I. Taubera and Kedarnath N. Sastrya ‘Departments of Medicine and Pathology, Boston University School of Medicine, Boston City Hospital, Boston, MA 02118, USA; and bApplied Immune Sciences, Inc., Santa Clara, CA 95054, USA. Tel. (l-408) 492- 9200 Received by J.A. Gorman: 11 June 1993; Revised/Accepted: 18 October/4 November 1993; Received at publishers: 6 December 1993 SUMMARY Bovine conglutinin (BC) is a C-type lectin isolated from bovine serum that appears to play a role in first-line host defense. The BC cDNA was cloned from a bovine liver library and the nucleotide (nt) sequence of 1519 bp was determined. The longest open reading frame encoded a 20-amino-acid (aa) signal sequence and a mature protein of 351 aa. Analysis of the nt and deduced aa sequences revealed 87 and 78% identity, respectively, with the sequences of another vertebrate lectin: bovine surfactant protein-D @P-D). Of interest, the expression of the BC mRNA, as determined by RNase protection assay, is restricted to liver, unlike bovine SP-D, a lung-surfactant protein. INTRODUCTION Bovine conglutinin (BC) is a Ca2+-dependent C-type lectin, first described in 1906 as a factor in bovine serum which strongly agglutinated ‘alexinated’ (antibody and complement-coated) erythrocytes (Bordet and Gay, 1906). Agglutination results from binding of BC to N- linked oligosaccharides on breakdown products of com- plement protein C3: iC3b, C3b and C3c (Hirani et al., 1985). The ability of BC to avidly bind N-linked carbohy- drates on C3 cleavage products generated during activa- Correspondence to: Dr. K.N.“Sastry, Department of Pathology, Boston University School of Medicine, 80 E. Concord St. S301, Boston, MA 02118, USA. Tel (1-617) 541-5646; Fax (1-617) 541-5636; e-mail: Bitnet:med9xwn@bucca.bu.edu Abbreviations: aa, amino acid(s); BC, bovine conglutinin; BC, gene (DNA, mRNA) encoding BC; bp, base pair(s); cDNA, DNA comple- mentary to RNA, kb, kilobase or 1000 bp; MBP, mannose-binding protein; nt, nucleotide(s); oligo, oligodeoxyribonucleotide; ORF, open reading frame; PCR, polymerase chain reaction; SP, surfactant protein; UTR, untranslated region(s). SSDI 0378-l 119(93)E0749-4 tion of the complement cascade has been widely used to detect and purify circulating immune complexes (McDougal and McDuffie, 1985). BC can bind oligosac- charide structures that have non-reducing terminal N- acetylglucosamine, mannose and fucose residues (Loveless et al., 1989). Structurally, the protein has a collagenous domain toward the N terminus, linked to a globular Cazf-dependent carbohydrate recognition domain. Hence it is placed in a family of C-type lectins called collectins (Malhotra et al., 1992; Sastry and Ezekowitz, 1993). Other members of the collectin family are mannose-binding protein (MBP) and the surfactant proteins (SP) A and D. Three 43-kDa BC polypeptide chains are joined together to form a basic structural unit; four such trimers are joined together by inter-chain disul- fide bridges (Strang et al., 1986). Recent studies have suggested a role for collectins in the first line of host defense against several classes of pathogens (for a review see Ezekowitz, 1991). For exam- ple, BC was shown to bind to oligosaccharides on the envelope glycoprotein, gp160, of HIV-l and inhibit its