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K Shigesada

Publications and source records attributed to K Shigesada.

67 records · Page 4Linked to original sources
PubMed1977

Isolation and characterization of conditional-lethal rho mutants of Escherichia coli.

Temperature-sensitive nitA (rho) mutants of E. coli were isolated; one of them was characterized as an amber mutant. These strains show the Nit phenotype (transcription of phage lambda DNA independent of the N gene) at low temperatures and are inviable at high temperatures. The mutated sites appear to be between cya and metE on the chromosome. Temperature-sensitive nitA bacteria not only permit leftward transcription of the lambda genome at a high rate in the absence of the lambda N protein, but also allow lambda growth at low temperatures. At high temperatures, phages lambda and T4 are incapable of normal development in these cells, while growth of T7 is not affected. The production of thermally unstable rho by the nitA temperature-sensitive mutant suggests that nitA is the structural gene for rho.

Anthranilate Synthase↗
PubMed1975

D-alpha-Hydroxyglutarate dehydrogenase of Rhodospirillum rubrum.

D-alpha-Hydroxyglutarate dehydrogenase of R. rubrum grown anaerobically in the light was partially purified and some properties were investigated. 1. The enzyme catalyze stoichiometrically the dehydrogenation reaction of D-alpha-hydroxyglutarate into alpha-oxoglutarate, coupled with the reduction of 2, 6-dichlorophenolindophenol. 2. Cytochrome c2, cytochrome c, and ferricyanide are effective as electron acceptors with the crude enzyme but not with the purified one, whereas NAD+ and NADP+ are completely ineffective. The enzyme is thought to play a role in the electron transport system of the organism. 3. D-alpha-Hydroxyglutarate is virtually the sole substrate for the enzyme. The apparent activity against L-alpha-hydroxyglutarate is presumed to be due to contamination of the L-isomer sample with the D-isomer. The enzyme shows barely detectable activity against both isomers of malate and virtually no activity against DL-lactate and glycolate. 4. Both isomers of malate and oxalate, which are presumably substrate analogues, inhibit the enzyme activity. 5. The enzyme is not an inducible enzyme but rather is a constitutive one for R. rubrum, unlike from the enzyme of Pseudomonas putida which is an inducible enzyme for the catabolism of lysine.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Overproduction of transcription termination factor Rho in Escherichia coli.

A plasmid system has been constructed which allows high-level expression of the rho gene of Escherichia coli under the control of the pL promoter and the N-antitermination regulatory system of bacteriophage lambda. The pL-directed synthesis of Rho crucially depends on the lambda N gene product and is promoted most effectively when this product is supplied from the N gene cloned on a separate compatible plasmid with a moderate copy number. The requirement for N can be circumvented partly, but not completely, by deletion of the region preceding the rho structural gene. Attempts were also made to optimize the construction of rho-expression plasmids by adjusting the orientation and location of pL and rho inserts on the pBR322 vector. With optimal conditions, Rho protein is overexpressed 100-fold and can become as much as 10% of the total cellular protein. Using this plasmid system, Rho can be purified with a yield of more than 20 mg from 10 g of induced cells.

Bacteriophage lambda↗