SUMMARYThirty-nine temperature-sensitive (ts) mutants that fail to grow at 39"5 °C but develop normally at 33 °C have been isolated from a nitrous-acid-treated stock of a wild-type strain of type 2 human adenovirus. The frequency of ts mutants among the surviving viruses was about IO %. Complementation tests in doubly infected cell cultures at restrictive temperature permitted the assignment of 19 of these mutants to I I complementation groups. They were characterized phenotypically according to their soluble capsid antigen production quantified by twodimensional immunoelectr0phoresis, virus DNA synthesis, as measured by alkaline sucrose gradient sedimentation of 34S DNA, and virion morphogenesis, as analysed by electron microscopy of cell sections. Two complementation groups were defective for DNA synthesis, four for soluble hexon production and two groups for total penton (penton base+fibre), while one group revealed no fibre production. Two complementation groups presented a normal antigen pattern, but the particles exhibited altered morphology as observed in cell sections.
Dimethyl-4,4'-dithiobisbutyrimidate dihydrochloride was used as a cleavable cross-linking reagent to maintain the structure of labile intermediates in adenovirus type 2 assembly. Analysis on sucrose gradients of nuclear adenovirus particles revealed two size classes, with sedimentation rates of 750 and 600S. After reversible fixation with diimido ester, the different classes were further separated on CsCl gradients and characterized with regard to their buoyant density, DNA content, and polypeptide composition. The 750S particles banded at 1.345 g/cm3 in CsCl, contained a DNA with a sedimentation coefficient of 34S in alkaline sucrose gradients, and had a polypeptide composition similar to that of young virions. The 600S population consisted of two types of particles with buoyant densities of 1.315 and 1.37 g/cm3. The 1.315-g/cm3 particles contained a DNA fragment of 7--11S and lacked the core proteins V and VII. In their place were found precursors P VI and P VIII and two nonvirion proteins with molecular weights of 50,000 (50K) and 39,000 (39K). 34S DNA was present in the 1.37-g/cm3 particles, which also lacked core proteins V and VII, as well as the 50K and 39K. Pulse-chase labeling kinetics suggested that the 1.315-g/cm3 particles were anterior to the 1.37-g/cm3 particles, themselves preceding the 1.345-g/cm3 young virions, and that the release of both 50K and 39K, possible scaffolding proteins, was required for entry of viral DNA.
Siderophore activity of Staphylococcus aureus was detected in an iron-restricted chemically defined medium. The molecular mass of this siderophore, called aureochelin, was 577 Da. Surface-associated proteins of 120, 88, 57, 35, and 33 kDa were mainly expressed under iron restriction conditions. Results showed a relationship between siderophore production and the existence of the 120-and 88-kDa proteins. Western blotting of surface-associated proteins revealed that these proteins were recognized both by patients sera and polyclonal rabbit serum.
The rabbit kidney does not readily metabolize but synthesizes glutamine at high rates by pathways that remain poorly defined. Therefore, the metabolism of variously labeled [13 C]-and [ 14 C]glutamates has been studied in isolated rabbit kidney tubules with and without acetate. CO 2 , glutamine, and alanine were the main carbon and nitrogenous end products of glutamate metabolism but no ammonia accumulated. Absolute fluxes through enzymes involved in glutamate metabolism, including enzymes of four different cycles operating simultaneously, were assessed by combining mainly the 13 C NMR data with a new model of glutamate metabolism. In contrast to a previous conclusion of Klahr et al. (Klahr, S., Schoolwerth, A. C., and Bourgoignie, J. J. (1972) Am. J. Physiol. 222, 813-820), glutamate metabolism was found to be initiated by glutamate dehydrogenase at high rates. Glutamate dehydrogenase also operated at high rates in the reverse direction; this, together with the operation of the glutamine synthetase reaction, masked the release of ammonia. Addition of acetate stimulated the operation of the "glutamate 3 ␣-ketoglutarate 3 glutamate" cycle and the accumulation of glucose but reduced both the net oxidative deamination of glutamate and glutamine synthesis. Acetate considerably increased flux through ␣-ketoglutarate dehydrogenase and citrate synthase at the expense of flux through phosphoenolpyruvate carboxykinase; acetate also caused a large decrease in flux through alanine aminotransferase, pyruvate dehydrogenase, and the "substrate cycle" involving oxaloacetate, phosphoenolpyruvate, and pyruvate.
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