The nucleotide sequence from the downstream region of the lux operon from the bioluminescent bacterium Photobacterium phosphoreum was determined. This area contains three genes involved in bioluminescence metabolism: luxF, luxE, and luxG. / LuxF is a new lux gene not found in the extensively studied luminescent bacteria of the Vibrio genus. The 26 kDa LuxF protein was found to be homologous to the 35 kDa $ beta$ subunit of bacterial luciferase (LuxB). LuxF is proposed to have arisen from luxB by a gene duplication event followed by deletion of 100 codons near the amino terminal. The LuxF protein was identified as the abundant non-fluorescent flavoprotein of unknown function found in many Photobacterium species. / LuxE codes for the 42 kDa fatty acyl-protein synthetase subunit of the fatty acid reductase complex which produces fatty aldehydes for the luciferase-catalyzed light-emitting reaction. This enzyme catalyzes the ATP-dependent activation of free fatty acids and covalently transfers acyl groups to other protein subunits via an intramolecular cysteine residue. Site-directed mutagenesis of five conserved cysteine residues has identified the site of fatty acyl transfer of the synthetase as Cys$ sp{364}.$ / LuxG is a new lux gene found in the operons of marine but not terrestrial luminescent bacteria. The 26 kDa LuxG protein was found to be highly homologous to an NAD(P)H:flavin oxidoreductase from Escherichia coli. The primary structure homologies implicate this new lux protein in flavin oxidoreduction biochemistry; a role in the luminescent-specific generation of the FMNH$ sb2$ cosubstrate of luciferase in the light-emitting reaction is likely. / Light emission was restored in dark V. harveyi fatty acid reductase mutants by complementation with V. harveyi and P. phosphoreum genes coding for the corresponding inactive enzyme subunit. The variation in fatty aldehyde- and fatty acid-stimulable in vivo luminescence with cell growth (and lux induction) shows that P. phosphoreum subunits interact poorly and in a protein concentration-dependent manner with V. harveyi fatty acid reductase complexes. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.39320 |
| Date | January 1992 |
| Creators | Soly, Robert Richard Roland |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001277595, proquestno: NN74810, Theses scanned by UMI/ProQuest. |
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