Post-Golgi protein traffic in the plant secretory pathway

The Golgi apparatus in plants is organized as a multitude of individual stacks that are motile in the cytoplasm and in close association with the endoplasmic reticulum (ER) (Boevink et al. in Plant J 15:441–447, 1998). These stacks operate as a sorting centre for cargo molecules, providing modification and redirection to other organelles as appropriate. In the post-Golgi direction, these include vacuole and plasma membrane, and specialized transport routes to each are required to prevent mislocalization. Recent evidence in plant cells points to the existence of post-Golgi organelles that function as intermediate stations for efficient protein traffic, as well as to the influence of small GTPases such as Rabs and ARFs on post-Golgi trafficking. This review focuses on the latest findings on post-Golgi trafficking routes and on the involvement of GTPases and their effectors on the trafficking of proteins in the plant secretory pathway. Sally L. Hanton and Loren A. Matheson have contributed equally to this work.     

Glycerol-induced formation of the molten globule from acid-denatured cytochrome c: implication for hierarchical folding

At high concentration (98% or higher, v/v), glycerol induces collapse of acid-denatured cytochrome c into a compact state, the G_U state, showing a molten globule character. The G_U state possesses a nativelike -helix structure but a tertiary conformation less packed with respect to the native state. The spectroscopic properties of the G_U state closely resemble those of the molten globule stabilized by the organic solvent from the native protein (called the G_N state), indicating that glycerol can stabilize the molten globule of cytochrome c either from the native or the acid-denatured protein. The G_U and the G_N states show spectroscopic (and, thus, structural) properties and stabilities comparable to those of molten globules stabilized by different effectors, despite the fact that the mechanisms involved in the molten globule formation may significantly differ. This implies in cytochrome c a hierarchy for the rupture (native-to-molten globule) or the formation (unfolded-to-molten globule) of intramolecular interactions leading to the stabilization of the molten globule state of the protein, independently from the effector responsible for the structural transition, in accord with the sequential model proposed by Englander and collaborators.     

Histochimie des colorations dans le bloc à base de métaux,application aux coupes semi-fines

Résumé Les auteurs décrivent une nouvelle méthode de coloration dans le bloc de tissu avec différents sels métalliques (alun de fer, tétroxyde d'osmium, acétate d'uranyl et chromeosmium) et l'hématoxyline. Cette technique est utilisée sur des tissus qui sont ensuite inclus en Araldit et permet d'obtenir des coupes semi-fines déjà colorées. Les auteurs ont cherché à préciser la spécificité de fixation du fer dans le tissu au moyen de méthodes d'extraction et de blocage. D'après leurs observations, le fer se fixerait aux groupes tissulaires chargés négativement. La nature des liaisons semble être de type électrostatique et complexe. Les liaisons complexes semblent prédominer au niveau des structures contenant des acides nucléiques.

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Histochemistry of block staining with metals for semifine sections

Summary The authors describe a new method of block staining for semifine sections with various metal salts (ferriammonium-sulphate, osmium tetroxyde, uranyl acetate, chromeosmium) and hematoxylin. They investigated the specificity of iron-alaun-hematoxylin with several extractions and blocking methods. According to their observations the dissociated iron is bounded to the negatively charged tissular groups. The nature of binding is thought to be electrostatic and coordinativ (complex). The last one is probably predominant in nucleic acids containing structures. This method seems to be encouraging for electron-histochemical investigations.

     

Studies on the possible biological effects of 50 Hz electric and/or magnetic fields: Evaluation of some glycolytic enzymes,glycolytic flux,energy and oxido-reductive potentials in human erythrocytes exposed in vitro to power frequency fields

An attempt has been made to understand whether 50 Hz electric and magnetic fields (EMFs) are involved in producing bioeffects by exposing human erythrocytes in vitro. The study evaluated some key glycolytic enzymes, glucose consumption, lactate production, energy charge, 2,3-diphosphoglycerate, and reduced glutathione levels. all of which are biochemical parameters significant to erythrocyte function. Cells exposed to individual or superimposed EMFs have not shown any significant difference compared with the controls. © 1993 Wiley-Liss. Inc.