Concepts and approaches towards understanding the cellular redox proteome

The physiological activity of a significant subset of cell proteins is modified by the redox state of regulatory thiols. The cellular redox homeostasis depends on the balance between oxidation of thiols through oxygen and reactive oxygen species and reduction by thiol-disulfide transfer reactions. Novel and improved methodology has been designed during recent years to address the level of thiol/disulfide regulation on a genome-wide scale. The approaches are either based on gel electrophoresis or on chromatographic techniques coupled to high end mass spectrometry. The review addresses diagonal 2D-SDS-PAGE, targeted identification of specific redox-interactions, affinity chromatography with thioredoxins and glutaredoxins, gel-based and non-gel based labelling techniques with fluorophores (such as Cy3, Cy5, ICy), radioisotopes, or with isotope-coded affinity tags (ICAT), differential gel electrophoresis (DIGE) and combined fractional diagonal chromatography (COFRADIC). The extended methodological repertoire promises fast and new insight into the intricate regulation network of the redox proteome of animals, bacteria, and plants.     

Changes in non-protein nitrogen metabolism during tobacco mosaic virus biosynthesis

1. Discs cut from tobacco leaf tissue infected with tobacco mosaic virus and cultured in water contain less non-protein nitrogen than comparable uninfected discs during the time at which TMV is formed. This deficiency disappears when virus formation ceases. Discs cultured in nutrient solution form about twice as much TMV as discs cultured in water. The maximum non-protein nitrogen deficiency is comparable in magnitude to the amount of virus synthesized. 2. The largest difference between injected and uninfected tissue occurs in the ammonia content. Smaller, but significant differences in amide content are found. Infected discs cultured in water show no significant differences from control discs in free amino acid content; infected discs cultured in nutrient solution develop a small deficiency in amino acid nitrogen. 3. The general patterns of change in composition of the pool of soluble nitrogen are similar in both infected and uninfected discs. 4. The data indicate that the bulk of the nitrogen incorporated into virus protein is withdrawn from the leaf's pool of soluble nitrogen; virus is formed de novo from ammonia nitrogen and non-nitrogenous carbon sources. The effect of virus infection on host nitrogen metabolism appears to be due to the formation of virus rather than to its presence.