Metalloenzymes

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Single Molecules Studies of Iron Hydrogenase

This project studies the mechanism of small molecule fixation in metalloenzymes focusing initially on hydrogen production. It is believed that more than three billion years ago, sulfate-reducing bacteria evolved a protein shell that enabled an iron- sulfur cluster to catalyze the oxidation of H2 abundant in earth’s atmosphere and derive energy; today we seek to understand and reverse this reaction to produce H2 as a chemical fuel. The hydrogenase from Clostridium pasteurianum, CpI, facilitates both electron and proton transfer at an iron-sulfur core to catalyze 2H+ + 2e- ⇌ H2. We wish to develop a model that rationalizes three length scales of reactivity: the structural and electronic changes of the iron-sulfur coordination complex; the domain- scale structural fluctuations of the apoprotein; and reagent exchange (protons, electrons, and molecular hydrogen) between the enzyme and the solvent. Single molecule spectroscopies, most prominently the new vibrational spectroscopies developed in this lab, will be used to probe these three coordinates in real time in a single enzyme.

  1. J. W. Peters, W. N. Lanzilotta, B. J. Lemon and L. C. Seefeldt, “X-ray Crystal Structure of the Fe-Only Hydrogenase (CpI) from Clostridium pasteurianum to 1.8 Angstrom Resolution,” Science, vol. 282, pp. 1853-1858, 1998. [Article]
  2. Z.-P. Liu and P. Hu, “A Density Functional Theory Study on the Active Center of Fe-Only Hydrogenase: Characterization and Electronic Structure of the Redox States,” J. Am. Chem. Soc., vol. 124, no. 18, pp. 5175-5182, 2002. [Article]
  3. Z.-P. Liu and P. Hu, “Mechanism of H2 metabolism on Fe-only hydrogenases,” J. Chem. Phys., vol. 117, no. 18, pp. 8177-8180, 2002. [Article]