The Rieske protein is found in the bc1complex of the electron transport chain, playing an important role in transporting electrons and protons. It contains a [2Fe-2S] cluster ligated by two cysteines and two histidines. The reduction potential of this cluster is pH-dependent and varies across species.  The H134C mutant of the Thermus thermophilus Rieske protein substitutes one of the ligating histidines for a cysteine, changing the ligation structure of the cluster from a 2Cys-2His ligation environment to a 3Cys-1His environment. To study the effects of this mutation, the protein was subjected to modification with diethyl pyrocarbonate (DEPC) at varying pH values. The behavior of this protein was observed and compared to a truncated form of the wild type protein through circular dichroism and UV visible spectroscopy. DEPC modification was observed in both wild type and H134C protein. H134C was also subjected to �-Mercaptoethanol and thiazolidinedione, which showed minimal change over time. In contrast, wild type Rieske showed lots of spectral change when exposed to �-Mercaptoethanol.   Because of the similarity in the iron-sulfur cluster ligands, H134C was also compared to another mitochondrial protein, mitoNEET, which contains a 3Cys-1His environment and has been classified as a diabetes drug activator. MitoNEET has been previously shown to be unstable at lower pH values, in contrast to H134C, which is stable at both low and high pH.  By comparing what is similar and what is different in the pH and chemical reactivity of H134C and MitoNEET, we can decipher what are common characteristics of the 3Cys-1His environment and what are unique properties of the different proteins.

Characterization of the H134C mutant of the <i>Thermus thermophius</i> Rieske protein

247th National Meeting (2014)

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Characterization of the H134C mutant of the Thermus thermophius Rieske protein