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61.
Coupled reductive and oxidative degradation of 4-chloro-2-nitrophenol by a co-immobilized mixed culture system 总被引:7,自引:0,他引:7
Summary The restriction of oxygen transfer in Ca-alginate beads used for the immobilization of microbial cells was applied to a coupled reductive and oxidative microbial degradation of the xenobiotic 4-chloro-2-nitrophenol (CNP). The conversion of CNP by Enterobacter cloacae under anaerobic conditions led to the formation of 4-chloro-2-aminophenol (CAP, 81%) and 4-chloro-2-acetaminophenol (CAAP, 16%) after 50 h incubation. CAP, the main reduction product, was further degraded under aerobic conditions by Alcaligenes sp. TK-2, a hybrid strain isolated by conjugative in-vivo gene transfer. Whereas both degradation steps excluded one another in homogeneous systems with free cells, a coupled reductive and oxidative degradation of CNP was observed in one aerated reactor system after co-immobilization of both strains in Ca alginate. The diameter of the alginate beads used for immobilization was recognized as one main factor determining the properties of this mixed culture system.
Offprint requests to: H.-J. Rehm 相似文献
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65.
The endoplasmic reticulum (ER) of the yeast Saccharomyces cerevisiae contains of proteolytic system able to selectively degrade misfolded lumenal secretory proteins. For examination of the components involved in this degradation process, mutants were isolated. They could be divided into four complementation groups. The mutations led to stabilization of two different substrates for this process. The mutant classes were called ''der'' for ''degradation in the ER''. DER1 was cloned by complementation of the der1-2 mutation. The DER1 gene codes for a novel, hydrophobic protein, that is localized to the ER. Deletion of DER1 abolished degradation of the substrate proteins. The function of the Der1 protein seems to be specifically required for the degradation process associated with the ER. The depletion of Der1 from cells causes neither detectable growth phenotypes nor a general accumulation of unfolded proteins in the ER. In DER1-deleted cells, a substrate protein for ER degradation is retained in the ER by the same mechanism which also retains lumenal ER residents. This suggests that DER1 acts in a process that directly removes protein from the folding environment of the ER. 相似文献
66.
The 13 kDa acidic seminal fluid protein (aSFP) is a major component of bovine semen exerting growth factor-like activity. The influence of the pure protein on sperm viability was observed by evaluating sperm motility using computer-assisted semen analysis. Furthermore, mitochondrial dehydrogenase activity as a parameter of sperm metabolism and the integrity of sperm membranes using a metal catalyzed lipid peroxidation assay were measured. Over a wide physiological range (0.003 to 4 g/l) aSFP did not influence motility and average-path velocity of sperm, but at the highest concentration (6 g/l) a significant reduction in motility could be observed. Mitochondrial activity was significantly stimulated at medium concentrations (0.125 to 2 g/l), whereas a 40% suppression was observed at maximum levels (4 g/l). A dose-dependent inhibition of lipid peroxidation could be demonstrated for medium and high concentrations of aSFP (0.125 to 4 g/l). Compared with other reducing agents, aSFP showed the highest potency in preventing oxidative stress. Such effects might be explained by the remarkable redox behavior of the protein. We suggest that in the bull aSFP may play a role in the regulation of sperm metabolism and the protection of sperm membranes from oxidative damage. 相似文献
67.
Insect immunity. A transgenic analysis in Drosophila defines several functional domains in the diptericin promoter. 总被引:4,自引:1,他引:3 下载免费PDF全文
Diptericins are antibacterial polypeptides which are strongly induced in the fat body and blood cells of dipteran insects in response to septic injury. The promoter of the single-copy, intronless diptericin gene of Drosophila contains several nucleotide sequences homologous to mammalian cis-regulatory motifs involved in the control of acute phase response genes. Extending our previous studies on the expression of the diptericin gene, we now report a quantitative analysis of the contribution of various putative regulatory elements to the bacterial inducibility of this gene, based on the generation of 60 transgenic fly lines carrying different elements fused to a reporter gene. Our data definitively identify two Kappa B-related motifs in the proximal promoter as the sites conferring inducibility and tissue-specific expression to the diptericin gene. These motifs alone, however, mediate only minimal levels of expression. Additional proximal regulatory elements are necessary to attain some 20% of the full response and we suspect a role for sequences homologous to mammalian IL6 response elements and interferon-gamma responsive sites in this up-regulation. The transgenic experiments also reveal the existence of a distal regulatory element located upstream of -0.6 kb which increases the level of expression by a factor of five. 相似文献
68.
Paramecium tetraurelia wild-type (7S) cells respond to 2.5 mm veratridine by immediate trichocyst exocytosis, provided [Ca2+]
o
(extracellular Ca2+ concentration) is between about 10–4 to 10–3
m as in the culture medium. Exocytosis was analyzed by light scattering, light and electron microscopy following quenched-flow/ freeze-fracture analysis. Defined time-dependent stages occurred, i.e., from focal (10 nm) membrane fusion to resealing, all within 1 sec.Veratridine triggers exocytosis also with deciliated 7S cells and with pawn mutants (without functional ciliary Ca channels). Both chelation of Ca2+
o
or increasing [Ca2+]
o
to 10–2
m inhibit exocytotic membrane fusion. Veratridine does not release Ca2+ from isolated storage compartments and it is inefficient when microinjected. Substitution of Na+
o
for N-methylglucamine does not inhibit the trigger effect of veratridine which also cannot be mimicked by aconitine or batrachotoxin. We conclude that, in Paramecium cells, veratridine activates Ca channels (sensitive to high [Ca2+]
o
) in the somatic, i.e., nonciliary cell membrane and that a Ca2+ influx triggers exocytotic membrane fusion. The type of Ca channels involved remains to be established.We thank Dr. C. Kung (Madison, WI) for providing the pawn mutant, Drs. G. Lehle and R. Waldschütz-Schüppel (Konstanz, Germany) for their help with light scattering experiments, and Ms. E. Dassler and D. Bliestle for continuous help during the extensive photographic documentation. This work has been supported by Deutsche Forschungsgemeinschaft, Schwerpunkt Neue mikroskopische Techniken für Biologie und Medizin (grant P178/11) and SFB156/B4. 相似文献
69.
The objective of this study was to investigate the in vitro and in vivo developmental abilities of equine embryos cryopreserved by vitrification. Twenty-eight embryos were recovered from Native pony and Thoroughbred mares at Days 5 to 7 by nonsurgical uterine flushing (detection of ovulation=Day 0). The vitrification solution contained 40% ethylene glycol, 18% Ficoll, and 0.3 M sucrose in PBS. The embryos were placed for 1 to 2 min in vitrification solution (Group 1) or following exposure to 20% ethylene glycol in PBS for 10 to 20 min (Groups 2 and 3). Single embryos were loaded in 0.25-ml straws, cooled for 1 min in liquid nitrogen vapor and immersed in liquid nitrogen. Straws were warmed in water (20 degrees C, 20 sec), and the contents were expelled with 0.5 M sucrose in PBS. Then the sucrose was diluted in 1-step (Groups 1 and 2) or 4-steps (Group 3). Embryos (n=21) were cultured for 120 h in TCM199 supplemented with 10% fetal bovine serum at 37 degrees C in 5% CO(2) in air and evaluated morphologically. Development to the hatching or hatched blastocyst stage was obtained in 0 7 , 4 7 and 4 7 embryos in Groups 1, 2 and 3, respectively. An additional 7 embryos were vitrified-warmed according to the treatment of Group 2 (4 embryos) and Group 3 (3 embryos). Five embryos were selected after in vitro culture for 4 h and were transferred nonsurgically into the uterine horn of Day-4 recipient mares. Transfer of 2 embryos (both Day-6 blastocysts: Group-2 treatment) resulted in pregnancies with a viable fetus at Day-60 of the gestation period. 相似文献
70.
Cytochrome-c reductase (EC 1.10.2.2.) from Solanum tuberosum L. comprises ten subunits with apparent molecular sizes of 55, 53, 51, 35, 33, 25, 14, 12, 11 and 10 kDa on 14% SDS-PAGE. The identity of the subunits was analysed by direct amino-acid sequencing via cyclic Edman degradation. A large-scale purification procedure for the enzyme complex based on affinity chromatography and gelfiltraton is described. All subunits were enzymatically fragmented and the generated peptides were separated by reverse-phase HPLC. Complete or partial sequence determination of 33 peptides comprising a total of nearly 500 amino acids showed, that cytochrome-c reductase from potato contains three respiratory proteins (cytochrome b, cytochrome c
1 and the Rieske iron-sulfur protein), four small proteins with molecular sizes below 15 kDa (so-called Q-binding, hinge, cytochrome-c
1-linked and core-linked proteins) and three proteins in the 50-kDa range which show similarity to members of the core/PEP/MPP protein family (core/processing enhancing protein/mitochondrial processing peptidase). In fact these subunits show highest sequence identity either to MPP or PEP, which is in line with earlier findings, that isolated cytochrome-c reductase from potato exhibits processing activity towards mitochondrial precursor proteins.Abbreviations MPP
mitochondrial processing peptidase
- PEP
processing enhancing protein
This research was supported by the Deutsche Forschungsgemeinschaft. 相似文献