Biosynthesis of the branched-chain amino acids in the cyanobacterium Synechocystis PCC6803: existence of compensatory pathways.
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.
Kouhen
Odile Maestri-El
OM
Laboratoire de Chimie Bactérienne-CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
Joset
Françoise
F
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
D000597:Amino Acids, Branched-Chain; D007532:Isoleucine; D007930:Leucine; D014633:Valine