Complete Nucleotide Sequence of the Mouse Lactate Dehydrogenase-a Functional Gene: Comparison of the Exon-Intron Organization of Dehydrogenase Genes

The complete sequence of 12,851 nucleotides of the mouse lactate dehydrogenase-A (LDH-A) gene has been determined. It includes eight exons, seven introns, promoter and regulatory regions. The B1 repetitive elements present in intron III and VI are oriented in opposite orientation, and they share 72% sequence homology. The exon-intron organization of mouse LDH-A gene is compared with the organizations of other dehydrogenase genes, and the molecular evolution of the nicotinamide adenine dinucleotide binding domains is discussed.     

Drug Stimulated DNA Cleavage Mediated by Cauliflower Topoisomerase II

We have investigated cauliflower (Brassica oleracea) topoisomerase II with respect to its interaction with DNA and demonstrate that the enzyme shares the characteristics of topoisomerase II purified from a variety of phylogenetically remote organisms. In the presence of the 2-nitroimidazole Ro 15-0216, cauliflower topoisomerase II-mediated DNA cleavage is extensively stimulated (approximately 20-fold) only at a site recognized as a major cleavage site for the enzyme in the absence of drug. The conservation of the enzyme's DNA specificity in the presence of Ro 15-0216 is in contrast to the effect exerted by traditional topoisomerase II inhibitors, which cause enzyme-mediated cleavage to take place at a multiple number of DNA sites. Ro 15-0216 may therefore prove useful as a tool in the elucidation of the enzyme's DNA interaction sites and its involvement in nucleic acid metabolism in plant cells.     

Mutation in Pseudomonas aeruginosa causing simultaneous defects in penicillin-binding protein 5 and in enzyme activities of penicillin release and D-alanine carboxypeptidase.

Penicillin-binding protein 5 in Pseudomonas aeruginosa had moderately penicillin-sensitive D-alanine carboxypeptidase activity. As in Escherichia coli, a defect in this enzyme activity was not lethal.     

Coordinate repression of arginine aminopeptidase and three enzymes of the arginine deiminase pathway in Streptococcus mitis

Streptococcus mitis contains two arginine aminopeptidases (I and II) as an arginine-supplying system and the arginine deiminase pathway as an arginine-utilizing system. The levels of arginine aminopeptidase I and three enzymes of the arginine deiminase pathway were suppressed by glucose in an apparently coordinate manner. Enzyme II appeared to be constitutive.     

Properties of soluble chromatins isolated from apical and axial parts of cauliflower inflorescence

Soluble chromatins were isolated from apical and axial parts of the cauliflower inflorescence. The template activities of the two chromatins were found to differ significantly, when using RNA polymerase of Escherichia coli. The derivative thermal melting profiles showed at least three melting peaks for each chromatin, indicating that higher T_m values could be distinguished in the apical chromatin in each peak. Histones extracted from both chromatins were analysed by acrylamide disc-electrophoresis. A much smaller amount of presumed F1 fraction was observed in the sample from axial chromatin.     

Regional replication of the bacterial chromosome induced by derepression of prophage lambda

Summary Derepression of prophage in E. coli strain K12 results in constitutive synthesis of the enzymes directed by the nearby bacterial operon, gal (escape synthesis). Phage 82 fails to cause escape synthesis despite that it lysogenizes the strain K12 at the site identical to that of on the host chromosome. The reason for the observed difference between 82 and is studied in the light of the recent finding that escape synthesis in -lysogen is closely associated to phage-promoted replication of bacterial chromosome contiguous to the prophage including gal operon (escape replication). Excision-defective mutants from 82, 82int or 82xis, do initiate escape synthesis, suggesting that the prophage 82 is normally excised too quickly after induction to allow sufficient escape replication. In support of this, much more DNA hybridizable to bacterial DNA contained in gal accumulates after induction of 82int than after induction of 82. Studies with various hybrid phages between 82 and have suggested: 1. The occurrence of gal escape synthesis depends on the nature of the region between b2 and N in the map. 2. Regions of the 82 genome on both sides of the attachment site contribute independently to prevent gal escape synthesis. Implications of these results are discussed with regard to the factors involved in the prophage excision.The IIIrd article of this series is in Molec. Gen. Genet. 159, 185–190 (1978)     

Chloroplast DNA topoisomerase I from cauliflower

An ATP-independent DNA topoisomerase has been isolated from chloroplasts of cauliflower leaves (Brassica oleracea var. botrytis) through DEAE-cellulose, AF-blue Toyopearl, and hydroxyapatite column chromatography. The sedimentation coefficient and Stokes radius of this enzyme are 3.6S and 3.6 nm, respectively, and the molecular weight of native enzyme is estimated to be 54,000. This enzyme changes the linking number in steps of one. The enzyme activity is stimulated by MgCl2, and this enzyme shows optimum activity at 30 degrees C in the range of 3 mM MgCl2 + 100 mM KCl-10 mM MgCl2 + 50 mM KCl. The enzyme activity was reduced remarkably by N-ethylmaleimide, indicating that a free sulfhydryl group is important for the activity; heparin and ellipticine also reduced the activity. Both cauliflower chloroplast topoisomerase and spinach chloroplast topoisomerase can relax positive supercoils as well as negative supercoils. From these properties, cauliflower chloroplast topoisomerase can be classified as a eukaryotic type I DNA topoisomerase.