CHARACTERIZATION OF THE POLYHYDROXYALKANOATE SYNTHASE GENE LOCUS OF RHODOBACTER-SPHAEROIDES

The Rhodobacter sphaeroides polyhydroxyalkanoate synthase structural g ene (phaC(Rs)) was identified as a 1,806-bp open reading frame. It enc oded a PHA synthase of 601 amino acids with a relative molecular mass of 66,742, which exhibited 25.9 to 39.0 % amino acid identity with PHA synthases from other bacteria. Enzymatic analysis, nucleotide sequenc e analysis, hybridization studies and analysis of Tn5-induced PHA-nega tive mutants provided multiple evidence that phaC(RS) represents a mon ocistronic operon and that phaC(Rs) is isolated in the genome from oth er genes known to be relevant for PHA metabolism. It is not clustered with the structural genes for beta-ketothiolase or pyridine nucleotide dependent acetoacetyl-CoA reductase.