Current Microbiology

, Volume 36, Issue 5, pp 253–258 | Cite as

Unusual Gene Arrangement of the Bidirectional Hydrogenase and Functional Analysis of Its Diaphorase Subunit HoxU in Respiration of the Unicellular Cyanobacterium Anacystis nidulans

  • Gudrun  Boison
  • Oliver  Schmitz
  • Barbara  Schmitz
  • Hermann  Bothe

Abstract.

The bidirectional, NAD+-dependent hydrogenase from cyanobacteria is encoded by the structural genes hoxFUYH, which have been found to be clustered, though interspersed with different open reading frames (ORFs), in the heterocystous, N2-fixing Anabaena variabilis and in the unicellular Synechocystis PCC 6803. In another unicellular, non N2-fixing cyanobacterium, Anacystis nidulans, hoxF has now been identified as being separated by at least 16 kb from the residual structural genes hoxUYH. An ORF (termed hoxE gene) is located immediately upstream of hoxF in A. nidulans and in Synechocystis. Its deduced amino acid sequence shows similarities to the NuoE subunit of NADH dehydrogenase I of E. coli, to the homologous subunit of respiratory complex I in mitochondria, and also to the first 104 amino acids of HoxF in A. nidulans and Synechocystis. The diversity in the arrangement of hydrogenase genes in cyanobacteria is puzzling. The subunits HoxE, HoxF, and HoxU of the diaphorase part of the bidirectional hydrogenase have been discussed to be shared both by respiratory complex I and bidirectional hydrogenase in cyanobacteria. Different hoxU mutants were obtained by inserting a lacZKmR cassette into the gene both in A. nidulans and Anacystis PCC 7942. Such mutants showed reduced H2-evolution activities catalyzed by the bidirectional hydrogenase, but had nonimpaired respiratory O2-uptake. A common link between respiratory complex I and the diaphorase part of the bidirectional hydrogenase in cyanobacteria may still exist, but this hypothesis could not be verified in the present study by analyzing defined mutants impaired in one of the diaphorase genes.

Keywords

Deduce Amino Acid Sequence Synechocystis Anabaena hoxE Gene NADH Dehydrogenase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York Inc. 1998

Authors and Affiliations

  • Gudrun  Boison
    • 1
  • Oliver  Schmitz
    • 1
  • Barbara  Schmitz
    • 1
  • Hermann  Bothe
    • 1
  1. 1.Botanisches Institut, Universität zu Köln, Gyrhofstr. 15, D-50923 Köln, Germany DE

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