title: The CD8alpha from sea bass (Dicentrarchus labrax L.): Cloning, expression and 3D modelling.
abstract: In this paper we describe the cloning, expression and structural study by modelling techniques of the CD8alpha from sea bass (Dicentrarchus labrax L.). The sea bass CD8alpha cDNA is comprised of 1490 bp and is translated in one reading frame to give a protein of 217 amino acids, with a predicted 26 amino acids signal peptide, a 88 bp 5'-UTR and a 748 bp 3'-UTR. A multiple alignment of CD8alpha from sea bass with other known CD8alpha sequences shows the conservation of most amino acid residues involved in the peculiar structural domains found within CD8alpha's. Cysteine residues that are involved in disulfide bonding to form the V domain are conserved. In contrast, an extra cysteine residue found in most mammals in this region is not present in sea bass. The transmembrane and cytoplasmic regions are the most conserved regions within the molecule in the alignment analysis. However, the motif (CXCP) that is thought to be responsible for binding p56lck is missing in the sea bass sequence. Phylogenetic analysis conducted using amino acid sequences showed that sea bass CD8alpha grouped with other known teleost sequences and that three different clusters were formed by the mammalian, avian and fish CD8alpha sequences. The thymus was the tissue with the highest CD8alpha expression, followed by gut, gills, peripheral blood leukocytes and spleen. Lower CD8alpha mRNA levels were found in head kidney, liver and brain. It was possible to create a partial 3D model using the human and mouse structures as template. The CD8alpha 11-120 amino acid region was taken into consideration and the best obtained 3D model shows the presence of ten beta-strands, involving about 50% of the sequence. The global structure was defined as an immunoglobulin-like beta-sandwich made of two anti-parallel sheets. Two cysteines were present in this region and they were at a suitable distance to form an S-S bond as seen in the template human and mouse structures.
authors.affiliation: Dipartimento di Scienze Ambientali, University of Tuscia, Largo dell'Università s.n.c., I-01100 Viterbo, Italy. fbuono@unitus.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Buonocore
authors.forename: Elisa
authors.initials: E
authors.lastname: Randelli
authors.forename: Steve
authors.initials: S
authors.lastname: Bird
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Secombes
authors.forename: Susan
authors.initials: S
authors.lastname: Costantini
authors.forename: Angelo
authors.initials: A
authors.lastname: Facchiano
authors.forename: Massimo
authors.initials: M
authors.lastname: Mazzini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Scapigliati
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001492:Bass / Q000235:genetics*; D016827:CD8 Antigens / Q000235:genetics*; D003001:Cloning, Molecular; D016000:Cluster Analysis; D017931:DNA Primers; D015870:Gene Expression; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D016827:CD8 Antigens; C431698:CD8alpha antigen; D017931:DNA Primers