Structure, molecular evolution, and gene expression of primate superoxide dismutases

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Background:

• Superoxide dismutases (SODs) are crucial antioxidant enzymes.
• Primate SOD evolution and gene expression patterns are not fully understood.

Purpose of the Study:

• To clone and analyze manganese (Mn-) and copper/zinc (Cu,Zn-) superoxide dismutase (SOD) cDNAs from eight primate species.
• To investigate the molecular evolution and gene expression of Mn- and Cu,Zn-SODs in primates.

Main Methods:

• Cloning of Mn- and Cu,Zn-SOD cDNAs from eight primate species.
• Comparative sequence analysis of protein-coding regions.
• Molecular evolutionary analyses, including phylogenetic tree construction and rate ratio calculations.
• Southern and Northern blot analyses to determine gene copy number and tissue-specific expression.

Main Results:

• Complete protein-coding sequences for Mn- and Cu,Zn-SODs were obtained and compared.
• Metal ligand residues were conserved; Cu,Zn-SOD showed more substitutions than Mn-SOD.
• Mn-SOD evolved at a constant rate, with its phylogeny mirroring primate evolutionary history.
• Cu,Zn-SOD evolution differed across lineages, with evidence of positive Darwinian selection in the great ape and human lineage.
• Primate Mn- and Cu,Zn-SOD genes appear to be single copies.
• Mn- and Cu,Zn-SOD expression was highest in the liver, kidneys, and adrenal glands of Japanese monkeys.

Conclusions:

• Mn-SOD evolution is highly conserved and reflects primate phylogeny.
• Cu,Zn-SOD evolution has been influenced by positive selection in the human lineage, suggesting adaptation.
• SOD genes are present as single copies in primates.
• Tissue-specific expression patterns indicate important roles for SODs in primate organs.