The reaction cycle of the reconstituted Sox enzyme system of Paracoccus pantotrophus requires the periplasmic proteins SoxYZ, SoxXA, SoxB, and SoxCD. The heme enzyme SoxXA covalently binds the sulfur substrate to the thiol of the single cysteine residue of SoxY located at its carboxy-terminal end. Bound sulfur is then oxidized to sulfate by a series of reactions. These involve sulfur dehydrogenase SoxCD which oxidizes the protein-bound sulfane sulfur to sulfone in a unique six-electron transfer. Bound sulfone is then hydrolyzed off by the sulfate thiohydrolase SoxB to regenerate SoxYZ. The flavoprotein SoxF enhances the rate of sulfur oxidation in vivo as evident from mutant analysis and we have specified its action in vitro. SoxYZ unlike the other Sox proteins is inactivated upon reduction. When the Sox system is reconstituted with inactivated SoxYZ, the thiosulfate-oxidizing activity is drastically decreased. SoxF reverses this inactivation and may mediate a conformational change of SoxYZ possibly by a transient interprotein disulfide. The membrane protein SoxV and the thioredoxin SoxS are essential for chemotrophic growth as evident from homogenote mutants defective in these proteins. Evidence is presented that both proteins transfer reductant from the cytoplasm to the periplasm and that SoxYZ is the final target of this transfer to balance the redox state of the Sox enzyme system or reduce a SoxY .. Y interprotein disulfide.
The development of Chironomus plumosus within the 4th larval instar was investigated under long day (18 h light/6 h dark) and short day (6/18) conditions at a temperature of 15°C. The state of the imaginal discs was the criterion of the state of development of the larvae.In general long day treatment induced subitaneous without delay development. Occasionally an endogenic developmental check, termed long day dormancy, occurred through long day treatment. Under long day conditions in the 4th larval instar only, the males developed faster on average than the females. The 4th larval instar was the most important in larval growth since about 80-85% of the maximum larval weight was formed during this period. By subitaneous development the weight of the larvae increased parallel to their respective development in both sexes.A developmental check, an oligopause, was induced by short day conditions. Its duration varied considerably but could last several months. In the majority of the larvae it ended spontaneously and metamorphosis began. The oligopause affected the imaginal disc phases 3-4 to 6. Under short day conditions the dormant larvae grew rapidly at first, but after some time their weights remained relatively constant, fluctuating only slightly around a mean value.When larvae of short day induced dormancy were placed under long day conditions, metamorphosis began immediately. Larvae kept individually developed more quickly than did those in a mass culture. A regulatory system of dormancy for Chironomus plumosus is proposed.
A. REIST UND J. FISCHER diesen Populationen untersucht werden, welches die Überwinterungsstadien sind. Reist, A and Fischer, J. 1979. "Ökologische und biometrische Untersuchungen an Chironomus-Larven (Diptera) des Wohlensees bei Bern." Revue suisse de zoologie 86, 893-899.
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