Interferon-gamma of the giant panda (Ailuropoda melanoleuca): complementary DNA cloning, expression, and phylogenetic analysis.

Interferon-gamma (IFN-gamma) is the only member of type II IFN and is vital in the regulation of immune and inflammatory responses. Herein we report the cloning, expression, and sequence analysis of IFN-gamma from the giant panda (Ailuropoda melanoleuca). The open reading frame of this gene is 501 base pair in length and encodes a polypeptide consisting of 166 amino acids. All conserved N-linked glycosylation sites and cysteine residues among carnivores were found in the predicted amino acid sequence of the giant panda. Recombinant giant panda IFN-gamma with a V5 epitope and polyhistidine tag was expressed in HEK293 host cells and confirmed by Western blotting. Phylogenetic analysis of mammalian IFN-gamma-coding sequences indicated that the giant panda IFN-gamma was closest to that of carnivores, then to ungulates and dolphin, and shared a distant relationship with mouse and human. These results represent a first step into the study of IFN-gamma in giant panda.