Succinate Transport in Escherichia coli Mutants Defective in Succinate Metabolism

To investigate the operation of a succinate transport system in Escherichia coli, mutants defective in succinate metabolism were isolated. Although the metabolic blocks in the mutant cells were not complete, the succinate transport assays became possible.

Pyruvate, lactate or many other carbon sources stimulated succinate uptake, and the uptake was strongly inhibited by some electron transport inhibitors, uncouplers of oxidative phosphorylation and sulfhydryl reagents. The mutant strains accumulated succinate into the cells against a concentration gradient when suitable energy sources were supplied.

Presence of glucose in the medium strongly repressed the formation of the succinate transport system. The optimum pH for the succinate uptake was between 7.8 and 8.0.     

Fractionation of Main Components and Their Subunits of Soybean Proteins

The water-extracted proteins, C and D fractions prepared from defatted soybean meals were fractionated by a method of gel filtration with Sephadex G–200, resulting in higher purification of the C and D components. The dissociated subunits of the C and D components were seen as bands B and B′ on the starch-gel electrophoretical pattern of system without urea. By the starch-gel electrophoresis in system with urea, the subunits of C component were mainly corresponding to the bands 7, 8 and 9, and those of the D component mainly to the band 10. Those subunits were fractionated by column chromatography on DEAE-cellulose contained urea.     

Age-Related Changes of Myelin Proteins in the Rat Peripheral Nervous System

Age-related changes in amounts of myelin proteins from rat sciatic nerve or spinal root were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). In the aged peripheral nerve myelin, the relative amounts of band 105K and proteins X and Y increased, whereas those of proteins P0 and P1 and band 190K decreased. Band 105K purified by preparative SDS-PAGE exhibited three bands of 105K, 28K, and 21K at the second electrophoresis. A repeated SDS-PAGE did not improve the purity of bank 105K, but increased the ratio of 21K to 28K. Compared with P0 protein, band 105K has a very similar peptide map pattern and amino acid composition, as well as the identical NH2 terminal residue, isoleucine. These findings suggest that band 105K is an aggregate form of P0 protein and its fragment, 21K. The 21K protein is a distinct entity from X protein. The quantitative and qualitative alterations in myelin proteins, as we report here, may reflect continuing demyelination and remyelination in aged peripheral nerves.     

Substrate Properties of Adenosine- and Uridine- 3′, 5′-bisphenylphosphonates for 3′-Nucleotidase/Nucleases

Abstract

3′, 5′-Bisphenylphosphonate and 5′-phenylphosphonate esters of adenosine and uridine were synthesized to investigate the substrate properties of the 3′, 5′-bisphenylphosphonates for 3′-nucleotidase/nucleases. The V _max/apparent K _m, values of the enzymes for them were found to be 9 to 21-fold higher than those for the corresponding nucleoside 3′-phenylphosphonates.     

Kinetochore stretching-mediated rapid silencing of the spindle-assembly checkpoint required for failsafe chromosome segregation

1. Download : Download high-res image (152KB)
2. Download : Download full-size image

     

Studies on Organic Insecticides

Insecticidally active sulfur derivatives (VI) of dihydronereistoxin (VIa) were synthesized in one step sequence starting from 2-dimethylamino-l,3-dichloropropane (III) or 1-dimethyl-amino-2,3-dichloropropane (IV) by utilizing intramolecular S_N 2 reaction.     

Stability and conformation of porcine phosphofructokinase M and L

1. The inactivation of porcine liver enzyme in the presence of urea proceeded more rapidly than that of porcine heart muscle enzyme. 2. The inactivation of both enzymes by urea was protected by allosteric activators, but inhibitors had no effect. 3. The circular dichroism spectrum of liver enzyme in the near ultraviolet region was markedly affected by urea, whereas that of heart muscle enzyme was not, except for the band at 255 nm.     

Simultaneous detection of histamine release and lactate production in rat mast cells induced by compound 48/80 using H NMR

¹H NMR spectroscopy was used to evaluate histamine release and lactate production in intact mast cells isolated from rats. The resonance lines of the aromatic histamine protons in mast cells, detected by the selective spin-excitation technique, were broader and located in a lower magnetic field than those in free histamine solution. When exocytosis of mast-cell granules was induced by compound 48/80, free histamine appeared, with a corresponding decrease in the amount of histamine in the mast cells; the lactate signal was also detected in the spectrum. On the addition of compound 48/80, there was a further release of histamine from mast cells, accompanied by further production of lactate. This result indicates that the mechanisms which induce the exocytosis of granules, and/or the events folowing exocytosis, activate glycolysis.