title: Biosynthesis of the branched-chain amino acids in the cyanobacterium Synechocystis PCC6803: existence of compensatory pathways.
abstract: Complementation of an E. coli mutant auxotrophic for the branched-chain amino acids (BCAA)--valine, leucine, and isoleucine--by the ilvG gene ( slr2088) of the cyanobacterium Synechocystis PCC6803 indicates that this gene encodes an active alpha-acetohydroxy acid synthase. Differences of response of the recombinants to the addition of the essential amino acids suggested a lower specificity for the initial reaction of the valine/leucine chain than for the isoleucine one. Inactivation of ilvG in Synechocystis led to a leaky phenotype, suggesting a capacity to compensate the auxotrophies by other processes. This observation is discussed in view of the general difficulty of obtaining auxotrophs in cyanobacteria.
authors.affiliation: Laboratoire de Chimie Bactérienne-CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Odile Maestri-El
authors.initials: OM
authors.lastname: Kouhen
authors.forename: Françoise
authors.initials: F
authors.lastname: Joset
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000096:biosynthesis*; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005816:Genetic Complementation Test; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D014633:Valine / Q000378:metabolism
chemical_list: D000597:Amino Acids, Branched-Chain; D007532:Isoleucine; D007930:Leucine; D014633:Valine