Cloning the trpR gene.

Summary In Escherichia coli, the structural gene for purine nucleoside phosphorylase, deoD, is subject to insertional inactivation by prophage . From one such secondary site lysogen, strain SP265, one may isolate deletions that remove all or part of the trpR gene and other genes in the deo-thr sector of the E. coli chromosome. Specialized transducing phages harboring serB ⁺ and trpR ⁺ were liberated following induction of SP265. All such phages were N-defective, bio-type pseudolysogens whose DNA persisted in the form of plasmids. A collection of transducing phages, differing in their complement of bacterial DNA, was used to locate cleavage sites for bamHI, SalI, and PvuI within the deoD-trpR region of the E. coli genome. The trpR gene lies within a specific 950 base pair BamHI-PvuI segment.A 1250 base pair BamHI fragment carrying a functional trpR gene was cloned into the amplifiable plasmid pBR322. A single SalI site in this fragment was shown to lie within the trpR gene.In two situations where increased gene dosage might generate elevated amounts of Trp repressor (N-defective trpR ⁺ pseudolysogens and strains harboring pBR322 trpR ⁺ plasmids) neither tryptophan auxotrophy, enhanced sensitivity to DL-5-methyltryptophan, nor super repression of the tryptophan biosynthetic enzymes was observed.Journal Paper No. 7426 of the Purdue University Agricultural Experiment Station     

Cloning, nucleotide sequence, and characterization of mtr, the structural gene for a tryptophan-specific permease of Escherichia coli K-12.

The mtr gene of Escherichia coli K-12 encodes an L-tryptophan-specific permease. This gene was originally identified through the isolation of mutations in the 69-min region of the chromosome, closely linked to argG. Cells with lesions in mtr display a phenotype of 5-methyltryptophan resistance. The mtr gene was cloned by using the mini-Mu system. The amino acid sequence of Mtr (414 codons), deduced by DNA sequence analysis, was found to be 33% identical to that of another single-component transport protein, the tyrosine-specific permease, TyrP. The hydropathy plots of the two permeases were similar. Possible operator sites for the tyrosine and tryptophan repressors are situated within the region of DNA that is likely to be the mtr promoter.     

Long-term platinum retention after treatment with cisplatin and oxaliplatin

Background  

The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin.     

Characterization of an HSP70 Cognate Gene Family in Arabidopsis

Analysis of the polypeptide composition of extracts from heat-shocked leaves of Arabidopsis indicated the presence of at least 12 HSP70-related polypeptides, most of which were constitutively expressed. In vitro translation of mRNA from heat-shocked and control leaves indicated that the amount of mRNA encoding four HSP70 polypeptides was increased strongly by heat-shock. Three Arabidopsis genes which exhibit homology to a Drosophila HSP70 gene were cloned. Two of the three genes are arranged in direct orientation approximately 1.5 kilobases apart. The third gene is not closely linked to the other two. Nucleotide sequence analysis of the 5′ regions of the two linked genes revealed that both contain a TATA box, the CAAT motif, and several short sequences which are homologous to the Drosophila heat-shock consensus sequence. The deduced partial amino acid sequence of the open reading frames were 79 and 72% homologous to the corresponding regions of the Drosophila HSP70-cognate and HSP70 sequences, respectively. As with the two maize HSP70 genes which have been characterized, and the Drosophila HSP70-cognate genes, the Arabidopsis genes contained a putative intron in the codon specifying amino acid 72. Analysis of mRNA levels with gene-specific oligonucleotide probes indicated that two of the genes were not expressed or were expressed at very low levels in leaves during normal growth or after heat-shock, whereas the other gene was constitutively expressed. By analogy with the results of similar studies of other organisms, it appears that the three cloned genes are members of a small family which are most closely related to the HSP70-cognate genes found in other species.