Molecular Cloning, Characterization and Predicted Structure of a Putative Copper-Zinc SOD from the Camel, Camelus dromedarius

摘要

Superoxide dismutase (SOD) is the first line of defense against oxidative stress induced by endogenous and/or exogenous factors and thus helps in maintaining the cellular integrity. Its activity is related to many diseases; so, it is of importance to study the structure and expression of SOD gene in an animal naturally exposed most of its life to the direct sunlight as a cause of oxidative stress. Arabian camel (one humped camel, Camelus dromedarius) is adapted to the widely varying desert climatic conditions that extremely changes during daily life in the Arabian Gulf. Studying the cSOD1 in C. dromedarius could help understand the impact of exposure to direct sunlight and desert life on the health status of such mammal. The full coding region of a putative CuZnSOD gene of C. dromedarius (cSOD1) was amplified by reverse transcription PCR and cloned for the first time (gene bank accession number for nucleotides and amino acids are JF758876 and AEF32527, respectively). The cDNA sequencing revealed an open reading frame of 459 nucleotides encoding a protein of 153 amino acids which is equal to the coding region of SOD1 gene and protein from many organisms. The calculated molecular weight and isoelectric point of cSOD1 was 15.7 kDa and 6.2, respectively. The level of expression of cSOD1 in different camel tissues (liver, kidney, spleen, lung and testis) was examined using Real Time-PCR. The highest level of cSOD1 transcript was found in the camel liver (represented as 100%) followed by testis (45%), kidney (13%), lung (11%) and spleen (10%), using 18S ribosomal subunit as endogenous control. The deduced amino acid sequence exhibited high similarity with Cebus apella (90%), Sus scrofa (88%), Cavia porcellus (88%), Mus musculus (88%), Macaca mulatta (87%), Pan troglodytes (87%), Homo sapiens (87%), Canis familiaris (86%), Bos taurus (86%), Pongo abelii (85%) and Equus caballus (82%). Phylogenetic analysis revealed that cSOD1 is grouped together with S. scrofa. The predicted 3D structure of cSOD1 showed high similarity with the human and bovine CuZnSOD homologues. The Root-mean-square deviation (rmsd) between cSOD1/hSOD1 and cSOD1/bSOD1 superimposed structure pairs were 0.557 and 0.425 A. The Q-score of cSOD1-hSOD1 and cSOD1-bSOD1 were 0.948 and 0.961, respectively.