tailieunhanh - Báo cáo khoa học: Expression of two [Fe]-hydrogenases in Chlamydomonas reinhardtii under anaerobic conditions

We have isolated and characterized a second [Fe]-hydro-genasegene fromthegreenalga,Chlamydomonas reinhardtii. TheHydA2gene encodes a protein of 505 amino acids that is 74% similar and 68% identical to the known HydA1 hydrogenase fromC. contains all the conserved residues and motifs found in the catalytic core of the family of [Fe]-hydrogenases. We demonstrate that both theHydA1and theHydA2transcripts are expressed upon anaerobic induction, achieved either by neutral gas purging or by sulfur deprivation of the cultures. . | Eur. J. Biochem. 270 2750-2758 2003 FEBS 2003 doi Expression of two Fe -hydrogenases in Chlamydomonas reinhardtii under anaerobic conditions Marc Forestier1 Paul King1 Liping Zhang1 Matthew Posewitz1 Sarah Schwarzer2 Thomas Happe2 Maria L. Ghirardi1 and Michael Seibert1 lNational Renewable Energy Laboratory Golden CO USA 2Ruhr-Universitaet-Bochum Lehrstuhl Biochemie der Pflanzen AG Photobiotechnologie Bochum Germany We have isolated and characterized a second Fe -hydro-genase gene from the green alga Chlamydomonas reinhardtii. The HydA2 gene encodes a protein of 505 amino acids that is 74 similar and 68 identical to the known HydA1 hydrogenase from C. reinhardtii. HydA2 contains all the conserved residues and motifs found in the catalytic core of the family of Fe -hydrogenases. We demonstrate that both the HydA1 and the HydA2 transcripts are expressed upon anaerobic induction achieved either by neutral gas purging or by sulfur deprivation of the cultures. Furthermore the expression levels of both transcripts are regulated in some cases differently by incubation conditions such as the length of anaerobiosis the readdition of O2 the presence of acetate and or the absence of nutrients such as sulfate during growth. Antibodies specific for HydA2 recognized a protein of about 49 kDa in extracts from anaerobically induced C. reinhardtii cells strongly suggesting that HydA2 encodes for an expressed protein. Homology-based 3D modeling of the HydA2 hydrogenase shows that its catalytic site models well to the known structure of Clostridium pasteurianum CpI including the H2-gas channel. The major differences between HydA1 HydA2 and CpI are the absence of the N-terminal Fe-S centers and the existence of extra sequences in the algal enzymes. To our knowledge this work represents the first systematic study of expression of two algal Fe -hydrogenases in the same organism. Keywords green algae anaerobic induction hydrogenase sulfur deprivation gene

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