Archives of Microbiology

, Volume 180, Issue 3, pp 194–203

Physiological role of the F420-non-reducing hydrogenase (Mvh) from Methanothermobacter marburgensis

  • Alexander Stojanowic
  • Gerd J. Mander
  • Evert C. Duin
  • Reiner Hedderich
Original Paper

DOI: 10.1007/s00203-003-0577-9

Cite this article as:
Stojanowic, A., Mander, G.J., Duin, E.C. et al. Arch Microbiol (2003) 180: 194. doi:10.1007/s00203-003-0577-9

Abstract

F420-non-reducing hydrogenase (Mvh) from Methanothermobacter marburgensis is a [NiFe] hydrogenase composed of the three subunits MvhA, MvhG, and MvhD. Subunits MvhA and MvhG form the basic hydrogenase module conserved in all [NiFe] hydrogenases, whereas the 17-kDa MvhD subunit is unique to Mvh. The function of this extra subunit is completely unknown. In this work, the physiological function of this hydrogenase, and in particular the role of the MvhD subunit, is addressed. In cells of Mt. marburgensis from Ni2+-limited chemostat cultures the amount of Mvh decreased about 70-fold. However, the amounts of mvh transcripts did not decrease in these cells as shown by competitive RT-PCR, arguing against a regulation at the level of transcription. In cells grown in the presence of non-limiting amounts of Ni2+, Mvh was found in two chromatographically distinct forms—a free form and in a complex with heterodisulfide reductase. In cells from Ni2+-limited chemostat cultures, Mvh was only found in a complex with heterodisulfide reductase. The EPR spectrum of the purified enzyme reduced with sodium dithionite was dominated by a signal with g zyx=2.006, 1.936 and 1.912. The signal could be observed at temperatures up to 80 K without broadening, indicative of a [2Fe–2S] cluster. Subunit MvhD contains five cysteine residues that are conserved in MvhD homologues of other organisms. Four of these conserved cysteine residues can be assumed to coordinate the [2Fe–2S] cluster that was detected by EPR spectroscopy. The MvhG subunit contains 12 cysteine residues, which are known to ligate three [4Fe–4S] clusters. Data base searches revealed that in some organisms, including the Methanosarcina species and Archaeoglobus fulgidus, a homologue of mvhD is fused to the 3′ end of an hdrA homologue, which encodes a subunit of heterodisulfide reductase. These data allow the conclusion that the only function of Mvh is to provide reducing equivalents for heterodisulfide reductase and that the MvhD subunit is an electron transfer protein that forms the contact site to heterodisulfide reductase.

Keywords

[NiFe] hydrogenases  Methanothermobacter marburgensis Heterodisulfide reductase Methanogenic archaea 

Abbreviations

Eha

Energy-converting hydrogenase A

Ehb

Energy-converting hydrogenase B

Frh

F420-reducing hydrogenase

Mvh

F420-non-reducing hydrogenase from Methanothermobacter

Vhc, Vhu

F420-non-reducing hydrogenases from Methanococcus voltae

Hdr

Heterodisulfide reductase

Hmd

H2-forming N5, N10methylenetetrahydromethanopterin dehydrogenase

Mc.

Methanococcus

Mp.

Methanopyrus

Ms.

Methanosarcina

Mt.

Methanothermobacter

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Alexander Stojanowic
    • 1
  • Gerd J. Mander
    • 1
  • Evert C. Duin
    • 1
    • 2
  • Reiner Hedderich
    • 1
  1. 1.Max-Planck-Institut für terrestrische MikrobiologieMarburgGermany
  2. 2.Department of ChemistryAuburn UniversityUSA

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