Expression cloning of an equine T-lymphocyte glycoprotein CD2 cDNA. Structure-based analysis of conserved sequence elements
Tavernor AS, Kydd JH, Bodian DL, Jones EY, Stuart DI, Davis SJ, Butcher GW. (1994), Eur J Biochem. 219, 969-76
An equine CD2 cDNA has been isolated by monoclonal antibody screening of a T-lymphocyte cDNA library. The cDNA contained an open reading frame of 1041 bp encoding a translated product of 347 amino acids. Northern blotting analysis revealed a single mRNA species expressed in spleen, thymus and activated peripheral lymphocytes. The predicted amino acid sequence has 50-65% identity with the human, rat and mouse CD2 sequences with greatest similarity shared with the human homologue. Evolutionarily conserved structural and functional domains in CD2 were identified by comparing the sequences of the equine, human, mouse and rat CD2 homologues in the context of the recently derived crystal structure of rat soluble CD2 [Jones, E. Y., Davis, S. J., Williams, A. F., Harlos, K. & Stuart, D. I. (1992) Nature 360, 232-239]. The key conserved features of the extracellular region included core residues necessary to preserve the structural integrity of the molecule, residues in the linker region likely to maintain the unique domain organization of CD2, an array of highly charged residues in the putative ligand-binding face of the molecule and glycosylation-signal distributions that render the putative ligand-binding GFCC’C” face of domain 1 relatively unhindered by glycosylation.
Key figure: Distribution of potential glycosylation sites.
The alignment in Fig. 3 was used to determine the location of the putative glycosylation sites for each of the CD2 homologues, and these were then mapped onto (a) a-carbon and (b) CPK representations of the rat sCD2 structure . The first N-acetylglucosamine residues of the putative oligosaccharides at each position are modelled as spheres of 0.36-nm radius coloured green (rat), yellow (mouse), red (human) and blue (equine). The view in (b) is centred on the GFCC’C” b-sheet of domain 1 as in Fig. 4.