Zhujun Chen

Publications (3)6.71 Total impact

• Article: Characterization of a cyanobacterial-like uptake [NiFe] hydrogenase: EPR and FTIR spectroscopic studies of the enzyme from Acidithiobacillus ferrooxidans.

  Olga Schröder, Boris Bleijlevens, Thyra E de Jongh, Zhujun Chen, Tianshu Li, Jörg Fischer, Jochen Förster, Cornelius G Friedrich, Kimberly A Bagley, Simon P J Albracht, Wolfgang Lubitz
  [show abstract] [hide abstract]
  ABSTRACT: Electron paramagnetic resonance (EPR) and Fourier transform IR studies on the soluble hydrogenase from Acidithiobacillus ferrooxidans are presented. In addition, detailed sequence analyses of the two subunits of the enzyme have been performed. They show that the enzyme belongs to a group of uptake [NiFe] hydrogenases typical for Cyanobacteria. The sequences have also a close relationship to those of the H(2)-sensor proteins, but clearly differ from those of standard [NiFe] hydrogenases. It is concluded that the structure of the catalytic centre is similar, but not identical, to that of known [NiFe] hydrogenases. The active site in the majority of oxidized enzyme molecules, 97% in cells and more than 50% in the purified enzyme, is EPR-silent. Upon contact with H(2) these sites remain EPR-silent and show only a limited IR response. Oxidized enzyme molecules with an EPR-detectable active site show a Ni(r)*-like EPR signal which is light-sensitive at cryogenic temperatures. This is a novelty in the field of [NiFe] hydrogenases. Reaction with H(2) converts these active sites to the well-known Ni(a)-C* state. Illumination below 160 K transforms this state into the Ni(a)-L* state. The reversal, in the dark at 200 K, proceeds via an intermediate Ni EPR signal only observed with the H(2)-sensor protein from Ralstonia eutropha. The EPR-silent active sites in as-isolated and H(2)-treated enzyme are also light-sensitive as observed by IR spectra at cryogenic temperatures. The possible origin of the light sensitivity is discussed. This study represents the first spectral characterization of an enzyme of the group of cyanobacterial uptake hydrogenases.
  JBIC Journal of Biological Inorganic Chemistry 03/2007; 12(2):212-33. · 3.29 Impact Factor
• Source

  Available from: montana.edu

  Article: Infrared studies of the CO-inhibited form of the Fe-only hydrogenase from Clostridium pasteurianum I: examination of its light sensitivity at cryogenic temperatures.

  Zhujun Chen, Brian J Lemon, Shan Huang, Derrick J Swartz, John W Peters, Kimberly A Bagley
  [show abstract] [hide abstract]
  ABSTRACT: Infrared spectroscopy has been used to examine the oxidized and CO-inhibited forms of Fe-only hydrogenase I from Clostridium pasteurianum. For the oxidized enzyme, five bands are detected in the infrared spectral region between 2100 and 1800 cm(-1). The pattern of infrared bands is consistent with the presence of two terminally coordinated carbon monoxide molecules, two terminally coordinated cyanide molecules, and one bridging carbon monoxide molecule, ligated to the Fe atoms of the active site [2Fe] subcluster. Infrared spectra of the carbon monoxide-inhibited state, prepared using both natural abundance CO and 13CO, indicate that the two terminally coordinated CO ligands that are intrinsic to the enzyme are coordinated to different Fe atoms of the active site [2Fe] subcluster. Irradiation of the CO-inhibited state at cryogenic temperatures gives rise to two species with dramatically different infrared spectra. The first species has an infrared spectrum identical to the spectrum of the oxidized enzyme, and can be assigned as arising from the photolysis of the exogenous CO from the active site. This species, which has been observed in X-ray crystallographic measurements [Lemon, B. J., and Peters, J. W. (2000) J. Am. Chem. Soc. 122, 3793], decays above 150 K. The second light-induced species decays above 80 K and is characterized by loss of the infrared band associated with the Fe bridging CO at 1809 cm(-1). Potential models for the second photolysis event are discussed.
  Biochemistry 03/2002; 41(6):2036-43. · 3.42 Impact Factor
• Article: Infrared studies of [Ni, Fe] hydrogenases and Fe-only hydrogenases at cryogenic temperatures : a thesis in Chemistry /

  Zhujun. Chen
  [show abstract] [hide abstract]
  ABSTRACT: Thesis (M.A.)--State University College at Buffalo, 2000. Includes bibliographical references (leaves 98-102).