Figure 5.

¹H NMR spectra of Zn₁Co₂ derivatives. (A) Wild-type BcII, (B) R121E BcII, and (C) R121H BcII. Spectra for wild type and R121H BcII were recorded in H₂O at 200 MHz and 298 K in 20 mM sodium succinate pH 6.0, 1 M NaCl. Resonances indicated with an asterisk are absent in spectra recorded in D₂O. Enzyme concentrations are 5 mM (wild type), 9 mM (R121H), and 6 mM (R121E), respectively. Samples were prepared by adding one Co(II) equivalent to the enzymes dialyzed extensively against the same buffer containing 20 μM Zn(II).