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Type II site-specific deoxyribonuclease Family members of this domain are Type II site-specific deoxyribonuclease EC=3.1.21.4. The endonuclease SmaI, recognizes and cleaves the sequence CCCGGGG on DNA, yielding a blunt end scission. It has been used for the diagnosis of neurogenic muscle weakness, ataxia and retinitis pigmentosa disease or Leigh's disease. Due to its specificity in recognizing the cleavage site, it is used in Leigh's disease to specifically eliminate the mutant mitochondrial DNA (mtDNA), which coexists with the wild-type mtDNA (heteroplasmy). Only the mutant mtDNA, but not the wild-type mtDNA, is selectively restricted by the enzyme. By delivering the SmaI gene fused to a mitochondrial targeting sequence, specific elimination of the mutant mtDNA was demonstrated, resulting in restoration of both the normal intracellular ATP level and normal mitochondrial membrane potential. The same strategy has also been demonstrated retinitis pigmentosa (NARP), where a mutant mitochondrial DNA carrying a T8993G transversion has been targeted by using SmaI enzymes. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",