Figure 1.

CPS-6 forms homodimers and degrades DNA into small fragments. (A) Wild-type CPS-6 was incubated with a 3′-end P³²-labeled single-stranded 14-nucleotide DNA that was degraded into small fragments (<7 nucleotides) as the concentration of CPS-6 was increased up to 0.8 μM. (B) Both the CPS-6 H148A and H148A/F122A mutants were eluted as homodimers in Superdex-75 size exclusion chromatography. (C) Plasmid nicking assays show that 87%, 18%, 32% and 8% of the supercoiled DNA was digested by wild-type CPS-6, H148A, F122A and H148A/F122A mutants, respectively.