Biomaterial Database

The pdx genetic marker adjacent to the chloramphenicol biosynthesis gene cluster in Streptomyces venezuelae ISP5230: functional characterization. 2001

N Magarvey, and J He, and K A Aidoo, and L C Vining

Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11.

The pdx-4 mutation in Streptomyces venezuelae ISP5230 confers a growth requirement for pyridoxal (pdx) and is a marker for the genetically mapped cluster of genes associated with chloramphenicol biosynthesis. A gene regulating salvage synthesis of vitamin B6 cofactors in S. venezuelae was cloned by transforming a pdx-4 mutant host with the plasmid vector pDQ101 carrying a library of wild-type genomic DNA fragments, and by selecting for complementation of the host's pdx requirement. However, the corresponding replicative plasmid could not be isolated. Southern hybridizations and transduction analysis indicated that the complementing plasmid had integrated into the chromosome; after excision by a second crossover, the plasmid failed to propagate. To avoid loss of the recombinant vector, a pdx-dependent Streptomyces lividans mutant, KAA1, with a phenotype matching that of S. venezuelae pdx-4, was isolated for use as the cloning host. Introduction of pIJ702 carrying an S. venezuelae genomic library into S. lividans KAA1, and selection of prototrophic transformants, led to the isolation of a stable recombinant vector containing a 2.5 kb S. venezuelae DNA fragment that complemented requirements for pdx in both S. venezuelae and S. lividans mutants. Sequence analysis of the cloned DNA located an intact ORF with a deduced amino acid sequence that, in its central and C-terminal regions resembled type-I aminotransferases. The N-terminal region of the cloned DNA fragment aligned closely with distinctive helix-turn-helix motifs found near the N termini of GntR family transcriptional regulators. The overall deduced amino acid sequence of the cloned DNA showed 73% end-to-end identity to a putative GntR-type regulator cloned in cosmid 6D7 from the Streptomyces coelicolor A3(2) genome. This location is close to that of pdxA, the first pdx marker in S. coelicolor A3(2) identified and mapped genetically in Sir David Hopwood's laboratory. The S. venezuelae gene and S. coelicolor pdxA are postulated to be homologues regulating vitamin B6 coenzyme synthesis from pdx.

UI	MeSH Term	Description	Entries
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010957	Plasmids	Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.	Episomes,Episome,Plasmid
D002701	Chloramphenicol	An antibiotic first isolated from cultures of Streptomyces venequelae in 1947 but now produced synthetically. It has a relatively simple structure and was the first broad-spectrum antibiotic to be discovered. It acts by interfering with bacterial protein synthesis and is mainly bacteriostatic. (From Martindale, The Extra Pharmacopoeia, 29th ed, p106)	Cloranfenicol,Kloramfenikol,Levomycetin,Amphenicol,Amphenicols,Chlornitromycin,Chlorocid,Chloromycetin,Detreomycin,Ophthochlor,Syntomycin
D005798	Genes, Bacterial	The functional hereditary units of BACTERIA.	Bacterial Gene,Bacterial Genes,Gene, Bacterial
D005809	Genes, Regulator	Genes which regulate or circumscribe the activity of other genes; specifically, genes which code for PROTEINS or RNAs which have GENE EXPRESSION REGULATION functions.	Gene, Regulator,Regulator Gene,Regulator Genes,Regulatory Genes,Gene, Regulatory,Genes, Regulatory,Regulatory Gene
D005810	Multigene Family	A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)	Gene Clusters,Genes, Reiterated,Cluster, Gene,Clusters, Gene,Families, Multigene,Family, Multigene,Gene Cluster,Gene, Reiterated,Multigene Families,Reiterated Gene,Reiterated Genes
D005816	Genetic Complementation Test	A test used to determine whether or not complementation (compensation in the form of dominance) will occur in a cell with a given mutant phenotype when another mutant genome, encoding the same mutant phenotype, is introduced into that cell.	Allelism Test,Cis Test,Cis-Trans Test,Complementation Test,Trans Test,Allelism Tests,Cis Tests,Cis Trans Test,Cis-Trans Tests,Complementation Test, Genetic,Complementation Tests,Complementation Tests, Genetic,Genetic Complementation Tests,Trans Tests
D005819	Genetic Markers	A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.	Chromosome Markers,DNA Markers,Markers, DNA,Markers, Genetic,Genetic Marker,Marker, Genetic,Chromosome Marker,DNA Marker,Marker, Chromosome,Marker, DNA,Markers, Chromosome
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial