Physiological roles of glutamine synthetases I and II in ammonium assimilation in Rhizobium sp. 32H1

The two glutamine synthetases of Rhizobium sp. 32H1 appear to be structurally and functionally distinct. Glutamine synthetase I was reversibly adenylylated, and its synthesis was repressed only twofold by ammonium. When in the unadenylylated configuration, it was the enzyme which allowed the organism to grow, albeit marginally, on ammonium as a nitrogen source. There is no evidence to suggest that the second enzyme, glutamine synthetase II, is regulated by adenylylation. However, this enzyme was repressed at least 50-fold by even low amounts of ammonium. Glutamine synthetase II does not seem to function in ammonium assimilation but rather in purine biosynthesis.     

X-linked dominant inheritance of partial phosphorylase kinase deficiency in mice

A new mouse strain, the V strain, with a partial deficiency of phosphorylase kinase has been established. The deficiency is caused by an X-linked dominant gene (Phk ^c ). Muscle extracts of homozygous and heterozygous females and hemizygous males have about 25% of the activity found in extracts of normal (C3H/HeHan) mice. This dominant phosphorylase kinase deficiency of the new V strain is different from that of the I-strain mice with the X-linked recessive deficiency of skeletal muscle phosphorylase kinase. The muscle extracts of V-strain and normal mice contain the same phosphorylase phosphatase activity of about 1 U/mg. Heart and liver extracts from V mice contained about 50% and 66%, respectively, of the phosphorylase kinase activity compared to that found in the same organs from the normal mice. The glycogen content of the skeletal muscle of the V strain was normal, i.e., 0.9 mg/g. Phosphorylase kinase was purified from the skeletal muscle of the V strain by (a) hydrophobic chromatography on methylamine Sepharose, (b) ammonium sulfate precipitation, and (c) gel filtration of Sepharose 4B. The enzyme has a similar structure to the normal murine and rabbit skeletal muscle enzyme, except that the proportion of the subunits differs. The molar ratio of the subunits of the V strain mice is (+)::=0.54:1:1.169, in comparison with that of the rabbit (+)::=1.1:1.0:1.0 and that of normal murine enzyme 0.9:1.0:0.7.This work was supported by the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen, West Germany and of the Fonds der Chemie, West Germany, and forms part of the md thesis of A. Vrbica.     

Labeling of cytochrome c oxidase with [35S]diazobenzenesulfonate. Orientation of this electron transfer complex in the inner mitochondrial membrane.

Isolated cytochrome c oxidase was fractionated by native-gel electrophoresis in Triton X-100, and a preparation of enzyme almost completely free of the usual impurities was recovered. This fraction was used to generate antibodies specific to cytochrome c oxidase. These antibodies inhibited cytochrome c oxidase activity rapidly and completely and immunoprecipitated an enzyme containing seven different subunits from detergent-solubilized mitochondria or submitochondrial particles. Reaction of detergent-solubilized cytochrome c oxidase with [35S]diazobenzenesulfonate labeled all seven subunits although I and VI were much less reactive than the other five components. When cytochrome c oxidase was immunoprecipitated from mitochondria which had been reacted with [35S]DABS, subunits II and III were the only components labeled. When the complex was immunoprecipitated from labeled submitochondrial particles, II, III, IV, V, and VII were all labeled. Polypeptides I and VI were not labeled from either side of the membrane. These results confirm earlier studies which showed that cytochrome c oxidase spans the mitochondrial inner membrane and is asymmetrically arranged across this permeability barrier.     

Fluorosugars inhibit biological properties of different enveloped viruses.

Both 2-deoxy-2-fluoro-D-glucose and 2-deoxy-2-fluoro-D-mannose were found to be potent inhibitors of the synthesis of infectious Semliki forest and fowl plague virus in chicken embryo cells and also of pseudorabies virus grown in rabbit kidney cells. It was found that the pseudorabies virus-mediated cell fusion and the synthesis of functional hemagglutinin of fowl plague virus were blocked. In all cases the 2-deoxy-2-fluoro-D-mannose-caused inhibition was stronger than the 2-deoxy-2-fluoro-D-glucose- or 2-deoxy-D-glucose-mediated blocks. Studies on the virus-specified proteins from Semiliki forest virus-infected cells grown in the presence of the inhibitors show that the target of the fluorosugar action, parallel to the well-studied effects of 2-deoxy-D-glucose, is the glycoprotein biosynthesis.     

Serum ferritin,cobalt excretion and body iron status.

Serum ferritin concentration was measured by immunoradiometric assay in 64 subjects. It was closely related to the size of body iron stores measured by hemosiderin content of bone marrow in all subjects and by the deferoxamine test in 10 patients with iron overload. Urinary cobalt excretion, an indirect measure of iron absorption, was inversely related to hemosiderin content of bone marrow in 34 patients aged 18 to 72 with or without liver disease, but this relation did not hold in a group of 20 student volunteers aged 17 to 30, indicating that the test is unreliable in young people. A strong inverse correlation was demonstrated between values for cobalt excretion and serum ferritin in the 34 patients and between those for iron absorption and serum ferritin in the 20 students. Serum ferritin concentration appears to reflect accurately the iron status of the healthy individual but high values in liver disease must be interpreted with caution.     

Phylogenetic position of Gluconobacter species as a coherent cluster separated from all Acetobacter species on the basis of 16S ribosomal RNA sequences

Abstract The 16S rRNA sequences from the Gluconobacter species G. asaii G. cerinus and G. frateurii were determined and compared with homologous sequences from published databases and sequences of G. oxydans and Acetobacter species previously described [Sievers M., Ludwig W. and Teuber M. (1994) System. Appl. Microbiol. 17, 189–196]. The Gluconobacter species have unique 16S rRNA sequences and exhibit sequence similarity values of 97.4 to 99.1%, corresponding to 36 to 14 base differences. The phylogenetic tree inferring methods (distance matrix, maximum parsimony and maximum likelihood) show that the species of Gluconobacter form a coherent, closely related cluster. Based on the distance matrix method including Rhodopila globiformis as an outgroup reference organism, Gluconobacter is well separated from Acetobacter .