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. 2013 Mar 5;18(4):266–277. doi: 10.1111/gtc.12040

Figure 2.

Figure 2

Unwinding polarity of replicative helicases. (A) Gram-negative bacteria E. coli and Helicobacter pylori helicase hexamer unwind double-stranded DNA in the direction of 5′ to 3′. Similarly, Gram-positive bacteria Bacillus anthracis and Bacillus stearothermophilus also showed a 5′ to 3′ unwinding activity. The DnaC helicase of Bacillus subtilis with 45% and 82% identical amino acid sequences to the counterpart in E. coli and Bacillus stearothermophilus, respectively, is speculated to have the same 5′ to 3′ helicase activity. Gram-positive Staphylococcus aureus DnaC helicase has 44% and 58% homology with E. coli DnaB and B. subtilis DnaC replicative DNA helicase, respectively, suggesting the same unwinding polarity as 5′ to 3′. (B) Both archaeal and eukaryotic CMG helicase complexes unwind double-stranded DNA in the direction 3′ to 5′.