title: Use of phi(glp-lac) in studies of respiratory regulation of the Escherichia coli anaerobic sn-glycerol-3-phosphate dehydrogenase genes (glpAB).
abstract: Expression of the glpA operon encoding the extrinsic membrane anaerobic sn-glycerol-3-phosphate dehydrogenase complex of Escherichia coli K-12 was studied in five strains carrying independent glpA-lac operon fusions. The location of the fusions was confirmed by transduction. Two of the strains produced an enzymatically active anaerobic sn-glycerol-3-phosphate dehydrogenase that accumulated in the cytoplasmic fraction of the cells. This suggests the loss of a specific membrane anchor subunit encoded by a distal gene, glpB, which was disrupted by the insertion. beta-Galactosidase in all five strains carrying phi(glpA-lac) was highly inducible by glycerol only anaerobically. A mutation in fnr, a pleiotropic activator gene, prevented full induction of the phi(glpA-lac), demonstrating that the Fnr protein is a positive regulator of the primary dehydrogenase as well as of the terminal reductases of anaerobic respiratory chains. Low concentrations of the respiratory poison KCN had a permissive effect on aerobic expression of phi(glpA-lac). Aerobic expression of the hybrid operon was also enhanced in isogenic derivatives of the fusion strains deficient in protoporphyrin biosynthesis (hemA). Thus, heme proteins may play a role in mediating aerobic repression of the anaerobic respiratory chain.
mesh_terms: D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005796:Genes; D005798:Genes, Bacterial; D005838:Genotype; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics*; D009154:Mutation; D009876:Operon; D010101:Oxygen Consumption; D010641:Phenotype; D013045:Species Specificity
chemical_list: D005993:Glycerolphosphate Dehydrogenase