The occurrence and relative positions of cysteine residues were investigated in proteins of various species. Considering random mathematical occurrence for an amino acid coded by two codons (3. 28%), cysteine is underrepresented in all organisms investigated. Representation of cysteine appears to correlate positively with the complexity of the organism, ranging between 2.26% in mammals and 0. 5% in some members of the Archeabacteria order. This observation, together with the results obtained from comparison of cysteine content of various ribosomal proteins, indicates that evolution takes advantage of increased use of cysteine residues. In all organisms studied except plants, two cysteines are frequently found two amino acid residues apart (C-(X)(2)-C motif). Such a motif is known to be present in a variety of metal-binding proteins and oxidoreductases. Remarkably, more than 21% of all of cysteines were found within the C-(X)(2)-C motifs in ARCHEA.: This observation may indicate that cysteine appeared in ancient metal-binding proteins first and was introduced into other proteins later.

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It is well established that the vacuole plays an important role in the cellular adaptation to growth in the presence of elevated extracellular Ca 2+ concentrations in Saccharomyces cerevisiae. The Ca 2+ ATPase Pmc1p and the Ca 2+ /H + exchanger Vcx1p/Hum1p have been shown to facilitate Ca 2+ sequestration into the vacuole. However, the distinct physiological roles of these two vacuolar Ca 2+ transporters remain uncertain. Here we show that Vcx1p can rapidly sequester a sudden pulse of cytosolic Ca 2+ into the vacuole, while Pmc1p carries out this function much less efficiently. This finding is consistent with the postulated role of Vcx1p as a high capacity, low affinity Ca 2+ transporter and suggests that Vcx1p may act to attenuate the propagation of Ca 2+ signals in this organism.z 1999 Federation of European Biochemical Societies.

The vacuole is the major site of intracellular Ca 2؉ storage in yeast and functions to maintain cytosolic Ca 2؉ levels within a narrow physiological range. In this study, we examined how cellular Ca 2؉ homeostasis is maintained in a vps33⌬ vacuolar biogenesis mutant. We found that growth of the vps33⌬ strain was sensitive to high or low extracellular Ca 2؉ . This strain could not properly regulate cytosolic Ca 2؉ levels and was able to retain only a small fraction of its total cellular Ca 2؉ in a nonexchangeable intracellular pool. Surprisingly, the vps33⌬ strain contained more total cellular Ca 2؉ than the wild type strain. Because most cellular Ca 2؉ is normally found within the vacuole, this suggested that other intracellular compartments compensated for the reduced capacity to store Ca 2؉ within the vacuole of this strain. To test this hypothesis, we examined the contribution of the Golgi-localized Ca 2؉ ATPase Pmr1p in the maintenance of cellular Ca 2؉ homeostasis. We found that a vps33⌬/pmr1⌬ strain was hypersensitive to high extracellular Ca 2؉ . In addition, certain combinations of mutations effecting both vacuolar and Golgi Ca 2؉ transport resulted in synthetic lethality. These results indicate that the Golgi apparatus plays a significant role in maintaining Ca 2؉ homeostasis when vacuolar biogenesis is compromised.

Major depressive disorder is a common and complex mental disorder with unknown etiology. GABAergic dysfunction is likely to contribute to the pathophysiology since disrupted GABAergic systems are well documented in depressed patients. Here we studied structural changes in the hippocampal GABAergic network using the chronic mild stress (CMS) model, as one of the best validated animal models for depression. Rats were subjected to 9 weeks of daily stress and behaviorally characterized using the sucrose consumption test into anhedonic and resilient animals based on their response to stress. Different subtypes of GABAergic interneurons were visualized by immunohistochemistry using antibodies for parvalbumin (PV), calretinin (CR), calbindin (CB), cholecystokinin (CCK), somatostatin (SOM), and neuropeptide Y (NPY). We used an unbiased quantification method to systematically count labeled cells in different subareas of the dorsal and ventral hippocampus. Chronic stress reduced the number of specific interneurons in distinct hippocampal subregions significantly. PV+ and CR+ neurons were reduced in all dorsal subareas, whereas in the ventral part only the CA1 was affected. Stress had the most pronounced effect on the NPY+ and SOM+ cells and reduced their number in almost all dorsal and ventral subareas. Stress had no effect on the CCK+ and CB+ interneurons. In most cases the effect of stress was irrespective to the behavioral phenotype. However, in a few specific areas the number of SOM+, NPY+, and CR+ neurons were significantly reduced in anhedonic animals compared to the resilient group. Overall, these data clearly demonstrate that chronic stress affects the structural integrity of specific GABAergic neuronal subpopulations and this should also affect the functioning of these hippocampal GABAergic networks.