The Rieske protein is an electron transport protein containing a [2Fe-2S] cluster ligated by 2 cysteines and 2 histidines. Proteins in the Rieske family share a common fold while demonstrating a range of reduction potentials, which are also pH-dependent.  The factors that tune the reduction potential are proposed to include the number of hydrogen bonds to, charges proximal to, and solvent accessibility of the ligands to the cluster. In order to probe these factors, mutants of the Thermus thermophilus Rieske protein were made. Y158F removed a hydrogen bond, while L135R and L135E added a positive or negative charge, respectively, proximal to the cluster. L135A increased the solvent exposure of the ligating histidine 134.  The pKa values of the wild type protein and the mutants were determined by pH titrations using UV-visible and circular dichroism spectroscopies.   Y158F, L135E, and L135A increased the pKa of the protein whereas L135R decreased the pKa.

Determining the pK<sub>a</sub> values of mutant Rieske proteins using pH-dependent UV-visible and circular dichroism spectroscopies

245th National Meeting (2013)

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Determining the pKa values of mutant Rieske proteins using pH-dependent UV-visible and circular dichroism spectroscopies

Determining the pK_a values of mutant Rieske proteins using pH-dependent UV-visible and circular dichroism spectroscopies