Figure 4.

The divalent metal specificity of CSP41. (A) A 0.5 µg aliquot of recombinant CSP41 was incubated with 20 fmol petDΔ18 RNA in buffer containing 20 mM concentrations of the indicated metals. Samples were removed after 10 min and analyzed in a 5% denaturing polyacrylamide gel. Sizes of CSP41 cleavage products are indicated on the left. (B) A 0.5 µg aliquot of recombinant CSP41 was incubated with 20 fmol petDΔ3 RNA in buffers containing varying concentrations of MgCl₂ as indicated. Each data point represents the average of duplicate measurements. The variation in the rate at each of the indicated Mg²⁺ concentrations was typically <10%. The curve represents the best fit to equation 1 (see Materials and Methods). (C) A 0.5 µg aliquot of recombinant CSP41 was incubated with 20 fmol petDΔ18 RNA in buffer containing 2 mM MgCl₂ and 20 mM of the indicated divalent metals. The control reaction (C) contained no CSP41. Reactions were stopped after 10 min and analyzed in a 5% denaturing polyacrylamide gel. Sites of CSP41 cleavage are indicated on the left.