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Cloning and characterization of the Bacillus subtilis hemEHY gene cluster, which encodes protoheme IX biosynthetic enzymes

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Author

Summary, in English

Mutations that cause a block in a late step of the protoheme IX biosynthetic pathway, i.e., in a step after uroporphyrinogen III, map at 94 degrees on the Bacillus subtilis chromosomal genetic map. We have cloned and sequenced the hem genes at this location. The sequenced region contains six open reading frames: ponA, hemE, hemH, hemY, ORFA, and ORFB. The ponA gene product shows over 30% sequence identity to penicillin-binding proteins 1A of Escherichia coli, Streptococcus pneumoniae, and Streptococcus oralis and probably has a role in cell wall metabolism. The hemE gene was identified from amino acid sequence comparisons as encoding uroporphyrinogen III decarboxylase. The hemH gene was identified by enzyme activity analysis of the HemH protein expressed in E. coli. It encodes a water-soluble ferrochelatase which catalyzes the final step in protoheme IX synthesis, the insertion of ferrous iron into protoporphyrin IX. The function of the hemY gene product was not elucidated, but mutation analysis shows that it is required for a late step in protoheme IX synthesis. The hemY gene probably encodes an enzyme with coproporphyrinogen III oxidase or protoporphyrinogen IX oxidase activity or both of these activities. Inactivation of the ORFA and ORFB genes did not block protoheme IX synthesis. Preliminary evidence for a hemEHY mRNA was obtained, and a promoter region located in front of hemE was identified. From these combined results we conclude that the hemEHY gene cluster encodes enzymes for the synthesis of protoheme IX from uroporphyrinogen III and probably constitutes an operon.

Publishing year

1992

Language

English

Pages

8081-8093

Publication/Series

Journal of Bacteriology

Volume

174

Issue

24

Document type

Journal article

Publisher

American Society for Microbiology

Topic

  • Microbiology

Keywords

  • Mutation
  • *Muramoylpentapeptide Carboxypeptidase
  • *Multigene Family
  • Multienzyme Complexes/genetics
  • Molecular Sequence Data
  • Humans
  • Hexosyltransferases/genetics
  • Heme/biosynthesis/*genetics
  • Genetic Complementation Test
  • Ferrochelatase/genetics
  • Bacterial
  • DNA
  • Molecular
  • Cloning
  • *Carrier Proteins
  • Northern
  • Blotting
  • Base Sequence
  • *Bacterial Proteins
  • Bacillus subtilis/*enzymology/*genetics
  • Amino Acid Sequence
  • Animals
  • Open Reading Frames
  • Operon
  • Penicillin-Binding Proteins
  • Peptidyl Transferases/genetics
  • Restriction Mapping
  • Sequence Homology
  • Amino Acid
  • Uroporphyrinogen Decarboxylase/genetics

Status

Published

Research group

  • Plant Biology

ISBN/ISSN/Other

  • ISSN: 0021-9193