Biosynthetic, Structural and Physiological Characterization of the Membrane Associated [NiFe] Hydrogenases in the Purple Sulfur Photosynthetic Bacterium, Thiocapsa Roseopersicina BBS

  • Prof Kornél Kovács, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Miss Judit Balogh, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Miss Tímea Balogh, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Dr Gergely Maróti, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Miss Andrea Nyilasi, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Ms Lívia Palágyi-Mészáros, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Mr Roalnd Tengölics, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary
  • Dr Gábor Rákhely, Department of Biotechnology, University of Szeged, Inst. Biophysics, Biol. Res. Centre, Hungarian Academy of Sciences, Hungary

    • Thiocapsa roseopersicina BBS, a purple sulfur photosynthetic proteobacterium, contains five [NiFe] hydrogenases: two membrane-bound (HupSL and HynSL) enzymes, two NAD+ reducing soluble (Hox1 and Hox2) hydrogenases and one soluble regulatory hydrogenase (HupUV).
    The structural genes (hynS, hynL) in the hyn operon are separated by a 2 kbp region containing two orfs: isp1 and isp2. In silico analysis revealed, that Isp1 is a cytochrome b like transmembrane protein, while Isp2 is a cytoplasmic protein belonging to the heterodisulfide reductase family. The in silico analysis of the recently sequenced T. roseopersicina genome and the functional analysis of the hynS-isp1-isp2-hynL genes suggested that the Hyn enzyme had connection to the sulfur metabolism and NAD+ house-keeping via the Isp1,2 proteins.
    Downstream of the hupSL genes several protein coding genes, localized on a single transcript were identified. Their protein products are involved in the posttranslational maturation, membrane anchoring of the enzyme, electron transport processes or transcriptional regulation. The physiological role of the HupSL enzyme is to reoxidize hydrogen. In this process, the cytochome b type HupC transfers the electron to the quinone pool.
    The maturation of the NiFe hydrogenases is a complex process requiring the concerted action of numerous accessory proteins affecting the biosynthesis of the various hydrogenases. The genes coding for these maturation enzymes were identified and a maturation model will be presented.

    This work has been partly supported by EU 6th Framework Programme projects (HyVolution SES6 019825 and NEST STRP SOLAR-H 5166510), and by domestic funds (NKTH, GVOP, Asbóth, Baross, DEAK-KKK, KN-RET)