Cloning and sequences analysis of the complement C3d cDNA of porcine, mouse and sheep.

The C3d gene from mouse,porcine and sheep were amplified from total RNA by RT-PCR using primes designed according to C3d gene sequences of human,mouse and cattle.The cDNA fragments were cloned and sequenced.Bioinformatics analyses showed that the C3d of mouse had a sequence similarity of 83 %,82 %and 81 % at the amino acid level with human,porcine and sheep C3d respectively,and the C3d of sheep shared 94 % similarity with cattle.The complement receptor2(CR2)-binding site on C3d of mouse,porcine and sheep was highly conserved,suggesting these receptor binding regions have consistent structure and function.