Genomics, phylogeny and in silico analysis of mitochondrial glutathione S transferase kappa from the camel Camelus dromedarius

The domesticated one-humped camel,

Camelus dromedarius, is one of the most important animals in the

Arabian Peninsula. For most of its life, this species is exposed to both intrinsic and extrinsic genotoxic

factors that cause gross DNA alterations in many organisms. GST enzymes constitute an important supergene

family involved in protection against the deleterious effects of oxidative stress and xenobiotics.

Cloning the camel mitochondrial GST kappa (GSTK) gene and comparing its structural similarities with

different species may aid in understanding its evolutionary relics. We cloned the camel GSTK using RTPCR.

This yielded an open reading frame of 678 nucleotides, encoding a protein of 226 amino acid residues.

In a comparative analysis, the cloned GSTK was used to screen orthologues from different organisms.

Phylogenetic analysis demonstrated that the camel GSTK apparently evolved from an ancestral GSTK gene

that predated the appearance of vertebrates, and it groupedwith pig, cattle, dog, horse, human and monkey

GSTKs. The calculated molecular weight of the translated ORF was 25.52 kDa and the isoelectric point

was 8.4. The deduced cGSTK sequence exhibited high identity with many mammals, such as Bactrian camel

(99.55%), pig, cattle and human (

>74%), and lower identity with other unrelated organisms, such as frog

(

Xenopus tropicalis, 61%), chicken (Gallus gallus, 57%), salmon (Salmo salar, 49%), sponge (Amphimedon

queenslandica

, 46%), tick (Amblyomma maculatum, 45%) and roundworm (Caenorhabditis elegans, 33%). A

3D structure was built based on the crystal structure of the human and rat enzymes. The levels of

cGSTK

expression in five camel tissues were examined via real-time PCR. The highest level of

cGSTK transcripts

was found in the camel liver, followed by the testis, spleen, kidney and lung.

داليا فؤاد محمد ابراهيم