title: Relationship between operon preference and functional properties of persistent genes in bacterial genomes.
abstract: BACKGROUND
  Genes in bacteria may be organised into operons, leading to strict co-expression of the genes that participate in the same operon. However, comparisons between different bacterial genomes have shown that much of the operon structure is dynamic on an evolutionary time scale. This indicates that there are opposing effects influencing the tendency for operon formation, and these effects may be reflected in properties like evolutionary rate, complex formation, metabolic pathways and gene fusion.
  
  
  RESULTS
  We have used multi-species protein-protein comparisons to generate a high-quality set of genes that are persistent in bacterial genomes (i.e. they have close to universal distribution). We have analysed these genes with respect to operon participation and important functional properties, including evolutionary rate and protein-protein interactions.
  
  
  CONCLUSIONS
  Genes for ribosomal proteins show a very slow rate of evolution. This is consistent with a strong tendency for the genes to participate in operons and for their proteins to be involved in essential and well defined complexes. Persistent genes for non-ribosomal proteins can be separated into two classes according to tendency to participate in operons. Those with a strong tendency for operon participation make proteins with fewer interaction partners that seem to participate in relatively static complexes and possibly linear pathways. Genes with a weak tendency for operon participation tend to produce proteins with more interaction partners, but possibly in more dynamic complexes and convergent pathways. Genes that are not regulated through operons are therefore more evolutionary constrained than the corresponding operon-associated genes and will on average evolve more slowly.
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7006 Trondheim, Norway.
authors.forename: Marit S
authors.initials: MS
authors.lastname: Bratlie
authors.forename: Jostein
authors.initials: J
authors.lastname: Johansen
authors.forename: Finn
authors.initials: F
authors.lastname: Drabløs
mesh_terms: D000465:Algorithms; D016000:Cluster Analysis; D055028:Comparative Genomic Hybridization; D019295:Computational Biology; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D023281:Genomics / Q000379:methods; D009876:Operon; D025941:Protein Interaction Mapping; D012269:Ribosomal Proteins / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D012269:Ribosomal Proteins