cDNA, genomic sequence cloning and overexpression of glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) from the Giant Panda

Abstract

GAPDH (glyceraldehyde-3-phosphate dehydrogenase) is a key enzyme of the glycolytic pathway and it is related to the occurrence of some diseases. The cDNA and the genomic sequence of GAPDH were cloned successfully from the Giant Panda (Ailuropoda melanoleuca) using the RT-PCR technology and Touchdown-PCR, respectively. Both sequences were analyzed preliminarily. The cDNA of GAPDH cloned from the Giant Panda is 1191 bp in size, contains an open reading frame of 1002 bp encoding 333 amino acids. The genomic sequence is 3941 bp in length and was found to possess 10 exons and 9 introns. Alignment analysis indicates that the nucleotide sequence and the deduced amino acid sequence are highly conserved in some mammalian species, including Homo sapiens, Mu musculus, Rattus norvegicus, Canis lupus familiaris and Bos taurus. The homologies for the nucleotide sequences of the Giant Panda GAPDH to that of these species are 90.67, 90.92, 90.62, 95.01 and 92.32% respectively, while the homologies for the amino acid sequences are 94.93, 95.5, 95.8, 98.8 and 97.0%. Primary structure analysis revealed that the molecular weight of the putative GAPDH protein is 35.7899 kDa with a theoretical pI of 8.21. Topology prediction showed that there is one Glyceraldehyde 3-phosphate dehydrogenase active site, two N-glycosylation sites, four Casein kinase II phosphorylation sites, seven Protein kinase C phosphorylation sites and eight N-myristoylation sites in the GAPDH protein of the Giant Panda. The GAPDH gene was overexpressed in E. coli BL21. The results indicated that the fusion of GAPDH with the N-terminally His-tagged form gave rise to the accumulation of an expected 43 kDa polypeptide. The SDS-PAGE analysis also showed that the recombinant GAPDH was soluble and thus could be used for further functional studies.