Hydrogen production in Chlamydomonas reinhardtii - new insights into the biochemistry of a photosynthetic FeFe-hydrogenase
Anja Hemschemeier, Martin Winkler, Jessica Jacobs, Sven Stripp, Ilka Czech and Thomas Happe
Ruhr Universität Bochum, Fakultät für Biologie und Biotechnologie, Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie, 44780 Bochum, Germany
Chlamydomonas has a highly active FeFe-hydrogenase, HydA1, which is located in the chloroplast stroma and which accepts electrons from the photosynthetic electron transport chain via ferredoxin. The alga has at least six ferredoxins, and one of these, Fdx5, accumulates strongly under anaerobic conditions (1), in which the hydrogenase is active. In order to gain deeper insights into ferredoxin-hydrogenase interaction, we have analyzed the interaction of wild type and site directed mutagenesis variants of HydA1 with ferredoxin PetF, both by in vitro tests and by a semi-natural PSI-dependent hydrogen production assay. We were able to identify the amino acids which are essential for a proper interaction of HydA1 and ferredoxin PetF (2). On the other hand, Fdx5, which we have characterized as being a plant-type ferredoxin with similar features as PetF, is not able to interact with HydA1 (1). We also had a closer look into the complex active site metal cluster of HydA1 (3) and got first insights into the mechanism by which the so-called H-cluster is attacked by oxygen (4). The results indicate that it might be possible to decrease or even abrogate the oxygen sensitivity of FeFe-hydrogenases, which is a requirement for applying the enzyme in (semi-) artificial devices for regenerative production of hydrogen gas.
(1) Jacobs J. et al. (2009) FEBS Lett 583: 325-329; (2) Winkler M. et al. (2009) J Biol Chem 284: 36620-36627; (3) Stripp S. et al. (2009a) Biochem 48: 5042-5049; (4) Stripp S.T. et al. (2009b) PNAS 106: 17331-17336
e-mail address of presenting author: anja.hemschemeier@rub.de
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