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A. Tyagi J. Hermans J. Steppuhn Ch. Jansson F. Vater R. G. Herrmann 《Molecular & general genetics : MGG》1987,207(2-3):288-293
Summary Several cDNA clones encoding the 33 kDa protein associated with the photosynthetic water oxidation activity of spinach were sequenced. A 1208 bp insert of one of the clones encodes the entire 331 amino acid residues of the precursor protein including 84 amino acids (8.5 kDa) of the amino-terminal transit peptide, 49 bp of the 5 and 111 bp of the 3 untranslated segment of the mRNA. The 3 poly(A) tail starts 19 bp downstream from a putative polyadenylation signal, TATAAA. The hydrophilic mature protein consists of 247 amino acid residues corresponding to an Mr of 26.5 kDa, which is 6.5 kDa smaller than the value determined by SDS-polyacrylamide gel electrophoresis (33–34 kDa), and shows a certain degree of conservation with the putative Mn-complexing active sites of bacterial Mn-dependent superoxide dismutases. The anatomy of the unusually long transit sequence is discussed with regard to current concepts of protein import into and protein routein within the organelle. 相似文献
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J. T. Keltjens J. M. H. Hermans G. J. F. A. Rijsdijk C. Van der Drift G. D. Vogels 《Antonie van Leeuwenhoek》1988,54(3):207-220
F430 is the prosthetic group of the methylcoenzyme M reductase of methanogenic bacteria. The compound isolated from Methanosarcina barkeri appears to be identical to the one obtained from the only distinctly related Methanobacterium thermoautotrophicum. F430 is thermolabile and in the presence of acetonitrile or C10
in4
sup-
two epimerization products are obtained upon heating; in the absence of these compounds F430 is oxidized to 12, 13-didehydro-F430. The latter is stereoselectively reduced under H2 atmosphere to F430 by cell-free extracts of M. barkeri or M. thermoautotrophicum. H2 may be replaced by the reduced methanogenic electron carrier coenzyme F420.Abbreviations CH3S-CoM
methylcoenzyme M, 2-methylthioethanesulfonic acid
- HS-CoM
coenzyme M, 2-mercaptoethanesulfonic acid
- F430
Ni(II) tetrahydro-(12, 13)-corphin with a uroporphinoid (III) ligand skeleton
- 13-epi-F430 and 12,13-di-epi-F430
the 12, 13- and 12, 13-derivatives of F430
- 12, 13-didehydro-F430
F430 oxidized at C-12 and C-13
- coenzyme F420
7,8-didemethyl-8-hydroxy-5-deazaflavin derivative
- coenzyme F420H2
reduced coenzyme F420
- MV+
methylviologen semiquinone
- HPLC
high-performance liquid chromatography 相似文献
6.
Jochen Tittgen Jürgen Hermans Johannes Steppuhn Thomas Jansen Christer Jansson Bertil Andersson Rachel Nechushtai Nathan Nelson Reinhold G. Herrmann 《Molecular & general genetics : MGG》1986,204(2):258-265
Summary Spinach cDNA libraries, made from polyadenylated seedling RNA, have been constructed in pBR322 and the expression vector gt11. Recombinant plasmids or phage for 14 intrinsic and peripheral thylakoid membrane proteins and one stromal protein have been identified. They encode components containing antigenic determinants against the lysine-rich 34 kd, the 23 kd and 16 kd proteins all associated with the water-splitting apparatus of the photosystem II reaction center, the ATP synthase subunits gamma, delta and CFo-II, the Rieske Fe/S protein of the cytochrome b/f complex, subunits 2, 3, 5 and 6 of the photosystem I reaction center, plastocyanin, ferredoxin oxidoreductase, chlorophyll a/b-binding apoproteins of the lightharvesting complex associated with photosystem II, and the small subunit of the stromal enzyme ribulose bisphosphate corboxylase/oxygenase. The cDNA inserts lack complementarity to plastid DNA but hybridize to restricted nuclear DNA as well as to discrete poly A+-mRNA species. The precursor products obtained after translation of hybrid selected RNA fractions in a wheat germ assay are imported and processed by isolated unbroken spinach chloroplasts. The imported components comigrate with the respective authentic proteins. 相似文献
7.
Maintenance of the cellobiose utilization genes of Escherichia coli in a cryptic state 总被引:6,自引:1,他引:5
The genes for cellobiose utilization are normally cryptic in Escherichia
coli. The cellobiose system was used as a model to understand the process
by which silent genes are maintained in microbial populations. Previously
reported was (1) the isolation of a mutant strain that expresses the
cellobiose-utilization (Cel) genes and (2) that expression of those genes
allows utilization of three beta- glucoside sugars: cellobiose, arbutin,
and salicin. The Cel gene cluster has now been cloned from that mutant
strain. In the course of locating the Cel genes within the cloned DNA
segment, it was discovered that inactivation of the Cel-encoded hydrolase
rendered the host strain sensitive to all three beta-glucosides as potent
inhibitors. This sensitivity arises from the accumulation of the
phosphorylated beta- glucosides. Because even the fully active genes
conferred some degree of beta-glucoside sensitivity, the effects of
cellobiose on a series of five Cel+ mutants of independent origin were
investigated. Although each of those strains utilizes cellobiose as a sole
carbon and energy source, cellobiose also acts as a potent inhibitor that
reduces the growth rate on glycerol 2.5-16.5-fold. On the other hand,
wild-type strains that cannot utilize cellobiose are not inhibited. The
observation that the same compound can serve either as a nutrient or as an
inhibitor suggests that, under most conditions in which cellobiose will be
present together with other resources, there is a strong selective
advantage to having the cryptic (Cel0) allele. In those environments in
which cellobiose is the sole, or the best, resource, mutants that express
the genes (Cel+) will have a strong selective advantage. It is suggested
that temporal alternation between these two conditions is a major factor in
the maintenance of these genes in E. coli populations. This alternation of
environments and fitnesses was predicted by the model for cryptic-gene
maintenance that was previously published.
相似文献
8.
The current system in Britain for compensating victims of medical injury depends on an assessment of negligence. Despite the sporadic pressure on the government to adopt a "no fault" approach, such as exists in Sweden, the negligence system will probably remain for the immediate future. The cost of this system was estimated to be 52.3m pounds for England 1990-1. The problem for the future, however, is one of forecasting accuracy at provider level: too high a guess and current patient care will suffer; too low a guess and future patient care will suffer. The introduction of a mutual insurance scheme may not resolve these difficulties, as someone will have to set the rates. Moreover, the figures indicate that if a no fault scheme was introduced the cost might be four times that of the current system, depending on the type of scheme adopted. 相似文献
9.
I. J. Hermans 《Neurochemical research》1978,3(6):711-724
-Glucosidase activity has been determined in homogenate and in centrifugation fractions of 7-day-old and adult rat brain; maximum activity was found at pH 4 and pH 5. Of the adult brain, more than 50% of the activity was concentrated in the 800-g sediment fraction (P1), while in the brain of 7-day-old rat about 20% was found in the corresponding fraction. The activity maximum in all fractions after a 2% Triton X-100 treatment occurs at pH 5. Addition of Triton to adult brain homogenate enhances the activity, but this stimulation is less than the sum of the activities observed at pH 4 and pH 5 in the absence of Triton. Triton addition to brain homogenate of 7-day-old rat results in a fall in activity at pH 4 and in a maximum at pH 5. In rat brain homogenate subjected to sonication, a loss of activity is observed at pH 4, scarcely at pH 5; the activity loss is completely abolished and turned into an increase under the influence of Triton. This increase equals the level obtained when Triton is added to an untreated brain homogenate. Sonication of rat brain homogenate leads to changes in the distribution pattern; about 25% of the activity of the adult brain is found in the P1 fraction compared to 50% in the corresponding fraction of the untreated brain. Fractionation of a sonicated brain homogenate from adult rat reveals that at pH 4 most activity (52%) is concentrated in the 20,000-g pellet (P2), 23% in supernatant fluid (S2); at pH 5 the opposite is observed: most activity (49%) is found in the 20,000-g supernatant (S2) and 23% in the 20,000-g pellet (P2). In the presence of Triton the activity of the sonicated brain homogenate of adult rat increases; this stimulation roughly equals the sum of the corresponding activities measured at pH 4 and pH 5 in the absence of Triton. 相似文献
10.
A. van Rotterdam F. H. Lopes da Silva J. van den Ende M. A. Viergever A. J. Hermans 《Bulletin of mathematical biology》1982,44(2):283-305
A linear spatially distributed model of a chain of neurons and interneurons was investigated in relation to the generation
of propagated alpha rhythmic activity. It was assumed that the elements of the chain were interconnected by means of recurrent
collaterals and inhibitory fibres in such a way that the connectivity functions were assumed to be homogeneous and their strength
was an exponentially decreasing function of distance. It was found that such a neuronal chain shows propagation properties
for frequencies in the alpha band. The results obtained with the model are in agreement with the phase velocities encountered
experimentally. In this way, it was possible to estimate the length of the neural fibres responsible for the phenomenon of
propagated activity. The estimates obtained are in good agreement with recent quantitative neuroanatomical data on the circuitry
of the neocortex. 相似文献