ABSTRACT
The degradation of PCB in soils by the biphenyl-utilising strain Alcaligenes xylosoxidans was studied in different soil types. In addition to the congener specificity, significant differences in the degradation of PCB by the strain in the different soil types were observed. Efficiency of degradation was generally better in sterilised soils, but the differences were not as significant as the differences observed between different soil types. These results indicate that the degradation of PCB is probably related not only to the capabilities of the strain employed and quality and amount of competitive species inhabiting the soils, but also to the soil sorption of the PCB congeners. Degradation is faster in the soils containing an intermediate amount of organic carbon with a high portion of total and aromatic carbon in humic acids.
Subject(s)
Alcaligenes/metabolism , Polychlorinated Biphenyls/metabolism , Alcaligenes/cytology , Biodegradation, Environmental , Cell Count , Chromatography, Gas , Humic Substances/metabolism , Reference Standards , Soil/analysis , Soil Microbiology , Soil Pollutants/metabolismABSTRACT
The VASI gene encoding the valyl-tRNA synthetase from yeast was isolated and sequenced. The gene-derived amino acid sequence of yeast valyl-tRNA synthetase was found to be 23% homologous to the Escherichia coli isoleucyl-tRNA synthetase. This is the highest level of homology reported so far between two distinct aminoacyl-tRNA synthetases and is indicative of an evolutionary relationship between these two molecules. Within these homologous sequences, two functional regions could be recognized: the HIGH region which forms part of the binding site of ATP and the KMSKS region which is recognized as the consensus sequence for the binding of the 3'-end of tRNA (Hountondji, C., Dessen, Ph., and Blanquet, S. (1986) Biochemie (Paris) 68, 1071-1078). Secondary structure predictions as well as the presence of both HIGH and KMSKS regions, delineating the nucleotide-binding domain and the COOH-terminal helical domain in aminoacyl-tRNA synthetases of known three-dimensional structure, suggest that the yeast valyl-tRNA synthetase polypeptide chain can be folded into three domains: an NH2-terminal alpha-helical region followed by a nucleotide-binding topology and a COOH-terminal domain composed of alpha-helices which probably carries major sites in tRNA binding.
Subject(s)
Amino Acyl-tRNA Synthetases/genetics , Escherichia coli/enzymology , Isoleucine-tRNA Ligase , Saccharomyces cerevisiae/enzymology , Valine-tRNA Ligase/genetics , Adenosine Triphosphate/metabolism , Amino Acid Sequence , Base Sequence , Binding Sites , Biological Evolution , Cloning, Molecular , DNA, Fungal/genetics , Protein Conformation , RNA, Transfer/metabolism , Saccharomyces cerevisiae/genetics , Sequence Homology, Nucleic AcidABSTRACT
The genes specifying the utilization of 3-chlorobenzoate by Pseudomonas sp. strain B13 WR1 have been cloned by using a broad-host-range cosmid cloning system. Analysis of the catabolic products of the enzymatic reactions encoded by two hybrid cosmids, pMW65 and pMW90, by thin-layer and high-performance liquid chromatography demonstrated that both encoded the genes for the complete catabolism of 3-chlorobenzoate. Physical analysis of one of the cosmid derivatives, pMW65, by restriction endonuclease mapping and subcloning demonstrated that the pathway genes are encoded on a fragment no larger than 11 kilobases.
