Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1777, Issue 5, Pages 410-416Publisher
ELSEVIER
DOI: 10.1016/j.bbabio.2008.02.002
Keywords
[FeFe]-hydrogenase; sulphur deprivation; green algae; purification; EPR
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Hydrogenase expression in Chlamydomonas reinhardtii can be artificially induced by anaerobic adaptation or is naturally established under sulphur deprivation. In comparison to anaerobic adaptation, sulphur-deprived algal cultures show considerably higher expression rates of the [FeFe]-hydrogenase (HydA1) and develop a 25-fold higher in vitro hydrogenase activity. Based on this efficient induction principle we have established a novel purification protocol for the isolation of HydA1 that can also be used for other green algae. From an eight liter C reinhardtii culture 0.52 mg HydA1 with a specific activity of 741 mu mol H-2 min(-1) mg(-1) was isolated. Similar amounts were also purified from Chlorococcum submarinum and Chlamydomonas moewusii. The extraordinarily large yields of protein allowed a spectroscopic characterization of the active site of these smallest [FeFe]-hydrogenases for the first time. An initial analysis by EPR spectroscopy shows characteristic axial EPR signals of the CO inhibited forms that are typical for the H-ox-CO state of the active site from [FeFe]-hydrogenases. However, deviations in the g-tensor components have been observed that indicate distinct differences in the electronic structure between the various hydrogenases. At cryogenic temperatures, light-induced changes in the EPR spectra were observed and are interpreted as a photodissociation of the inhibiting CO ligand. (c) 2008 Elsevier B.V. All rights reserved.
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