Conservation in decay accelerating factor (DAF) structure among primates

The decay accelerating factor (DAF, CD55) protects self cells from activati on of autologous complement on their surfaces, It functions to disable the C3 convertases, the central amplification enzymes of the cascade, Its activ e site(s) are contained within four similar to 60 amino acid long units, te rmed complement control protein repeats (CCPs). which are suspended above t he cell surface on a 68 amino acid long serine/threonine (S/T)-rich cushion that derives from three exons. We previously proposed a molecular model of human DAF's four CCPs in which certain amino acids were postulated to be r ecognition sites for the interaction between DAF and the C3 convertases. In the current study, wt characterized DAF in five non-human primates: the gr eat apes, gorilla and common chimpanzee, and the Old World monkeys: hamadry as baboon, Rhesus macaque, and patas monkey. Amino acid homology to human D AF was approximately 98% for the two great apes and 83% for the three Old W orld monkeys. The above cited putative ligand interactive residues were fou nd to be fully conserved in all of the non-human primates, although there w ere amino acid changes outside of these areas, In the chimpanzee, alternati ve splicing of the S/T region was Found potentially to be the source of mul tiple protein isoforms in erythrocytes, whereas in the patas monkey, simila r alternative splicing was observed but only one protein band was seen. Int erestingly, a Rhesus macaque was found to exhibit a phenomenon paralleling the human Cromer Dr(a-) blood group, in which a 44-base pair deletion in CC P3 leads to a frameshift and early STOP codon. (C) 2000 Elsevier Science Lt d. All rights reserved.