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1.
The physical origin and functional significance of the near infra-red light scattering changes observable upon flash illumination of diluted suspensions of magnetically oriented, permeabilised frog retinal rods has been reinvestigated with particular attention paid to the degree with which transducin remains attached to the membrane. In the absence of GTP, the so called binding signal is shown to include two components of distinctive origins, widely different kinetics, and whose relative amplitudes depend on the dilution of the suspension and resulting detachment of transducin from the disc membrane. The fast component is a consequence of the fast interaction between photoexcited rhodopsin (R*) and the transducin remaining on the membrane. Its kinetics monitors a structural modification of the discs caused by a change in electrostatic interaction between closely packed membranes upon the formation of R*-T complexes. The slow component monitors the slow rebinding to the membrane and possible subsequent interaction with excess R* of T-GDP which, in spite of its low solubility, had eluted into solution given the high dilution of the permeated rods. In the presence of GTP, the so called dissociation signal includes a fast, anisotropic release component that specifically monitors the release into the interdiscal space of T
-GTP formed from the membrane-bound pool, and a slower isotropic loss component monitoring the leakage from the permeated rod of the excess T
-GTP which did not interact with the cGMP phosphodiesterase. The amplitudes of both components depend exclusively on the membrane bound T-GDP pool. The kinetics of the loss component is limited by the size and degree of permeation of the rod fragments, rather than by the dissociation rate of T
-GTP from the membrane.Abbreviations ROS
rod outer segment
- R
rhodopsin
- R*
photoactivated rhodopsin
-
T, T-GDP, T
-GDP, T
-GTP, T
transducin and its various forms
-
T
mb, T
sol: T
bound to membrane or soluble
- PDE
cGMP-phosphodiesterase
- GTP
guanosine 5-triphosphate
- GDP
guanosine 5-diphosphate
- GDP S
guanosine 5-O-(2-thiodiphosphate)
- cGMP
guanosine-3-5 cyclic-monophosphate
- DTT
dithiothreitol
- HEPES
4-(2-hydroxyethyl)-1-piperazine-ethane sulfonic acid
- TRIS
Tris (hydroxymethyl)aminomethane
- SDS
sodium dodecyl sulfate 相似文献
2.
Jacques Raymond Brahim Mimouni Jean-Louis Azanza 《Plant Systematics and Evolution》1994,193(1-4):69-79
The seed storage globulins from sixHelianthus and four hybrids were studied using mono and bidimensional gel SDS electrophoresis (+ 2 mercaptoethanol). The polypeptide composition of each subunit was determined. Different pairs are specifically expressed according to the species studied. Three typical patterns were discriminated. All the studied species exhibit five subunits: two of them are expressed in all the species (11 and 22). The subunit corresponding to the 11 pair is present inH. petiolaris and in the three populations ofH. annuus studied. The 2b2 pair is common toH. annuus andH. argophyllus. H. petiolaris presents two specific 2a2 and 44 pairs andH. annuus a specific 33 pair. InH. argophyllus 11 33 or 44 are never observed but are replaced by 13 and 31 pairs. Some globulins, poorly represented, are of forms but present chains of higher molecular weights (in the range 54–56 kDa). Expressing variations in the banding patterns between these species by the use of a similarity index reveals complete identity between the three populations ofH. annuus. Identity between the twoH. petiolaris studied is also observed.H. annuus andH. argophyllus appear to be closer to each other thanH. petiolaris concerning the seed storage globulins. 相似文献
3.
Keshava Nagalakshmi Zhou Gu Spruill Michelle Ensell Mang Ong Tong-man 《Molecular and cellular biochemistry》2001,222(1-2):69-76
Occupational exposure to beryllium (Be) and Be compounds occurs in a wide range of industrial processes. A large number of workers are potentially exposed to this metal during manufacturing and processing, so there is a concern regarding the potential carcinogenic hazard of Be. Studies were performed to determine the carcinogenic potential of beryllium sulfate (BeSO4) in cultured mammalian cells. BALB/c3T3 cells were treated with varying concentrations of BeSO4 for 72 h and the transformation frequency was determined after 4 weeks of culturing. Concentrations from 50–200 g BeSO4/ml, caused a concentrationdependent increase (9–41 fold) in transformation frequency. Nontransformed BALB/c3T3 cells and cells from transformed foci induced by BeSO4 were injected into both axillary regions of nude mice. All ten Beinduced transformed cell lines injected into nude mice produced fibrosarcomas within 50 days after cell injection. No tumors were found in nude mice receiving nontransformed BALB/c3T3 cells 90 days postinjection. Gene amplification was investigated in Kras, cmyc, cfos, cjun, csis, erbB2 and p53 using differential PCR while random amplified polymorphic DNA fingerprinting was employed to detect genomic instability. Gene amplification was found in Kras and cjun, however no change in gene expression or protein level was observed in any of the genes by Western blotting. Five of the 10 transformed cell lines showed genetic instability using different random primers. In conclusion, these results indicate that BeSO4 is capable of inducing morphological cell transformation in mammalian cells and that transformed cells induced by BeSO4 are potentially tumorigenic. Also, cell transformation induced by BeSO4 may be attributed, in part, to the gene amplification of Kras and cjun and some BeSO4induced transformed cells possess neoplastic potential resulting from genomic instability. 相似文献
4.
Ducks were chronically implanted with thermodes in the POAH region, the lower brainstem or the vertebral canal. At thermoneutral conditions, lowering the temperature of the spinal cord (Tvc) or the lower brainstem (Tmb) stimulated metabolic heat production (M) with a subsequent rise of core temperature (Tc). Lowering the temperature of the POAH region (Thy) induced a fall of Tc due to paradoxical activation of heat defence and, thus, induced slight to moderate general hypothermia depending on the cooling intensity. When Thy was normalized, the hypothermia temporarily stimulated metabolic heat production until Tc was normalized. Cold sensitivity of the entire body, as revealed by the metabolic response to the hypothermia induced by preceding POAH cooling, and cold sensitivity of the spinal cord and the lower brainstem, as revealed by the metabolic response to local cooling, were quantified by calculating the quotient M/T from the maximum metabolic response and the experimentally induced drop of Tc, Tmb and Tvc. With lower brainstem cooling M/Tmbdid not exceed –0.4 W/(kg · C). With spinal cord cooling, M/Tvc did not exceed –0.6 W/(kg · C). The mean value of M/Tc after hypothermia induced by POAH cooling was –4.02 W/(kg · C). The results indicate that the cold sensitivity residing in the CNS of ducks represents only a small fraction of the entire cold sensitivity of the body.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, Israel. 相似文献
5.
Zusammenfassung Durch eine anaerobe Mischflora aus Ackerboden wurde -Hexachlorcyclohexan (-HCH) in 4–5 Tagen zu 90% abgebaut. Dabei erfolgte eine schnelle Abspaltung des Chlors in Form von Chloridionen und danach eine Freisetzung des C- und H-Anteiles in Form flüchtiger Verbindungen, in denen kein Chlor und auch kein CO2 nachzuweisen war.Die Verwendung von 14C/3H- und 36Cl/3H-doppelmarkiertem -HCH zeigte, daß die Cl- und H-Abspaltung nicht im Verhältnis von 1:1 erfolgte, sondern mehr Cl als H abgespalten wurde. Die flüchtigen Verbindungen enthielten andererseits höhere 14C- als 3H-Anteile. Gaschromatographische Untersuchungen zeigten ebenfalls eine rasche Verminderung des -HCH und die Bildung verschiedener Metabolite. Es wurde jedoch kein -Pentachlorcyclohexen nachgewiesen. Bei steigenden O2-Gehalten in der Gasphase verminderte sich der -HCH-Abbau. Jedoch fanden auch noch bei 5% O2 Chlorabspaltung und die Freisetzung flüchtiger Metabolite statt.-HCH wurde ebenfalls, jedoch langsamer, durch die anaerobe Mischflora abgebaut. Auch hier wurde Chlorid abgespalten, und es traten ebenfalls flüchtige Verbindungen auf, die kein Chlor enthielten.
Degradation of 14C-, 3H- and 36Cl-labelled -hexachlorocyclohexane by anaerobic soil microorganisms
Up to 90% of the -Hexachlorocyclohexane (-HCH) applied to an anaerobic mixed bacterial flora enriched from an arable soil were degraded within 4–5 days. Degradation resulted in a rapid release of chloride and in formation of chlorine-free volatile metabolites. CO2 formation from the molecule was not detected.Investigations with 14C/3H- and 36Cl/3H double-labelled -HCH indicated that the release of Cl and H did not occur in the ratio of 1:1. More Cl than H was split off. The volatile compounds contained more 14C than 3H. Gas chromatographic studies also showed the rapid decrease of -HCH and the formation of several metabolites. -Pentachlorocyclohexene was not detected. Increasing O2-contents in the gas phase of cultures resulted in decreases of the compound's degradation. Release of chloride and of volatile metabolites were observed with O2 contents in the gas phase up to 5%.-HCH was also, but more slowly as with -HCH, degraded by the anaerobic mixed flora. Chloride was released and volatile, chlorine-free metabolites were found.相似文献
6.
Zusammenfassung Die Anthocynsyanthese des Senfkeimlings ist phytochromabhängig. Lediglich zwei Gewebe, die Epidermis der Cotyledonen und die Subepidermis des Hypocotyls sind zu dieser Anthocyansynthese fähig. Erst 24 Std nach Aussaat ist Anthocyansynthese möglich und bereits etwa 60 Std nach Aussaat (25° C; Standardbedingungen vgl. Methoden) erlischt dei Fähigkeit zur Anthocyansynthese weitgehend und zwar unabhängig von der Menge des synthetisierten Anthocyans. Die höchste Empfindlichkeit für Licht besitzt das Anthocyan bildende System etwa 36 Std nach Aussaat. — Teilt man den Keimling unmittelbar vor der Anthocyanmessung in 4 Segmente auf (Abb. 9) und mißt den Anthocyangehalt der Segmente getrennt, so stellt sich heraus, daß die Fähigkeit zur Anthocyansynthese im mittleren und basalen Bereich des Hypocotyls rapide verloren geht. Im oberen Hypocotylabschnitt hingegen und in den Cotyledonen nimmt diese Fähigkeit erst zu, und die Abnahme ist langsamer. —Es werden Argumente für die Auffassung entwickelt, daß das spezifische und dynamische Zellmuster, das man hinsichtlich der P730-abhängigen Anthocyansynthese vorfindet, ein Ausdruck der primären Differenzeierung sei (vgl. Abb. 4). P730 hingegen, so stellen wir uns vor, wirkt unspezifisch im Rahmen einer sekundären Differenzierung, indem es potentiell aktive Gene (P730) in Funktion setzt. Welche Gene in den einzelnen Zellen des Dunkelkeimlings potentiell aktiv sind, legt die primäre Differenzierung fest. — Diese Vorstellungen werden durch den Befund gestützt, daß eine Applikation von Actinomycin D zu einer zeitlich sehr viel ausgedehnteren Anthocyansynthese führt; offenbar deshalb, weil die genetisch kontrollierte Entwicklung des primären Differenzie-rungsmusters gebremst wird. Eine Folge wäre, daß die Inaktivierung der zur Anthocyansynthese benötigten Gene, die normalerweise etwa 60 Std nach Aussaat erfolgt, weit hinausgezögert wird.
Primary and secondary differentiation in connection with photomorphogenesis of seedlings (Sinapis alba L.)
Summary Anthocyanin synthesis of the mustard seedling (Sinapis alba L.), a typical phytochrome-dependent photoresponse has been further investigated. — It has been found that only two types of tissue can synthesize anthocyanin under the influence of active phytochrome (=P730), namely, the epidermis of the votyledons and the subepidermal layer in the hypocotyl (Fig. 2, 3). — Under our standard conditions (25° C; cf. methods) phytochrome-potentiated anthocyanin synthesis is only possible 24 hours after sowing and it ceases about 60 hours after sowing, independent of the amount of anthocyanin which has been accumulated (Fig. 5, 6). On the basis of the whole seedling the highest sensitivity of the anthocyanin producing system to light is around 36 hours after sowing (Fig. 8). Within the tissues which are capable of forming anthocyanin there is a characteristic shift of the ability to respond to P730 as the seedling ages. If we devide the seedling into 4 segments (Fig. 9) it turns out that in the basal and middle part of the hypocotyl the ability to form anthocyanin is rapidly lost whereas in the upper part of the hypocotyl and in the cotyledons this ability even increases at first. The following decrease is slower than in the basal parts (Fig. 10, 11).It is argued that this specific and dynamic cellular pattern of responsiveness to P730 can be regarded as a manifestation of a primary differentiation in the course of which the genotype of each individual cell in the dark-grownt seedling is devided into 3 functional types of genes: active, inactive, and potentially active genes (P730) (Fig. 4). — In connection with anthocyanin synthesis P730 is thought to act exclusively at the level of secondary differentiation, i.e., it is thought to initiate the action of potentially active genes via a signal-chain. The action of P730 is non-specific. The specificity of the photoresponse of an individual cell is determined by the status of its primary differentiation (Fig. 4).If the process of differentiation is slowed down (e.g. by the application of low doses of Actiomycin D) anthocaynin synthesis can continue much longer than under our standard conditions where it ceases around 60 hours after sowing (Fig. 12). This fact seems to indicate that the loss of the ability to form anthocyanin is due to an inactivation of pertinent genes by the process of primary differentiation, which is itself, as one would expect, under the control of genes.相似文献
7.
Willem J. Stiekema Freek Heidekamp Jeanine D. Louwerse Harrie A. Verhoeven Paul Dijkhuis 《Plant cell reports》1988,7(1):47-50
Tuber discs of Solanum tuberosum cv Bintje and Désirée were cocultivated with an Agrobacterium tumefaciens binary vector, carrying both the neomycine phosphotransferase and the E. coli -glucuronidase gene fused to resp. the nopaline synthase and Cauliflower mosaic virus 35S promotor.Inoculated tuber discs produce transgenic shoots in selective media containing kanamycin. The transgenic plants are phenotypically normal and contain the euploid number of chromosomes. Both the neomycin phosphotransferase as well as the -glucuronidase gene are expressed conferring resp. kanamycin resistance and -glucuronidase activity to the plants.Abbreviations GUS
-glucuronidase
- NPT
neomycin phosphotransferase
- CaMV
Cauliflower Mosaic Virus
- BAP
6-benzylaminopurine
- GA3
gibberellic acid
- NAA
naphthalineacetic acid
- LB
Luria Broth
- MU
methylumbelliferone 相似文献
8.
A -carotene oxygenase is described which occurs in the Cyanobacterium Microcystis. It cleaves -carotene and zeaxanthin specifically at the positions 7,8 and 7,8, while echinenone and myxoxanthophyll are not affected. The oxidative cleavage of -carotene leads to the formation of -cyclocitral and crocetindial and that of zeaxanthin to hydroxy--cyclocitral and crocetindial in nearly stoichiometric amounts. Oxidant is dioxygen as has been demonstrated by high incroporation (86%) of 18O2 into -cyclocitral. -Carotene oxygenase is membrane bound, sensitive to sulfhydryl reagents, antioxidants and chelating agents. Iron seems to be an essential part of the enzyme activity. Cofactors necessary for the reaction could not be detected.Abbreviations TLC
thin layer-chromatography
- PIPES
piperazine-N,N-bis-(2-ethanesulfonate) Na
- TES
2{[tris-(hydroxymethyl)-methyl]-amino} ethanesulfonic acid
Dedicated to Professor G. Drews on occasion of his 60th birthday 相似文献
9.
Charles W. Bacon Dorothy M. Hinton William J. Chamberlain William P. Norred 《Journal of Plant Growth Regulation》1994,13(2):53-57
The de novo induction of roots in tomatoes (Lycopersicon esculentum) Mill. cvs. Earlypak-7, Ace, Better Boy, Roma, and Parks' Whopper by fumonisin B1, a mycotoxin produced by Fusarium moniliforme J. Sheld., was studied. In graded dosages of fumonisin B1, detached stems of the cultivars Ace, Better Boy, and Roma were induced to produce calluses and roots earlier than controls. The cultivar Ace was especially responsive to this mycotoxin, and following a single application, callus initiation was observed to occur within a 24–48-h period and roots were produced as early as 72 h with 10 g/shoot or as late as 96 h with low dosages. The control plants of all cultivars were completely negative for a rooting response during this time. Some cultivars treated with fumonisin B1 showed either no response or developed signs of phytotoxicity. Those cultivars that were stimulated to produce roots did not show signs of phytotoxicity, except at dosages of 0.5 mg/plant and higher. One cultivar did not show any signs of phytotoxicity nor was it induced to root. The ability of fumonisin B1 to affect the accumulation of calcium in other systems, and its structural similarity to sphingosine suggest that the induction of adventitious roots may be a calcium-dependent process. 相似文献
10.
Rectal and vaginal temperature responses of the Savanna Brown goat indigenous to the Nigerian guinea savanna were determined during the harmattan and the hot-dry season. Measurements were made at 06:00h and at 14:00h after 8h exposure to field conditions. At the 06:00h measurements during the harmattan, all animals were observed to shiver. A significant (P<0.01) positive correlation was found between rectal (Tre) and vaginal temperatures. During the harmattan, mean Tre was 38.2C at 06:00h and 39.7C at 14:00h; the mean difference, Tre was 1.5C. During the hot-dry season, Tre at 06:00h was 38.1C, and at 14:00h, 38.7; Tre was 0.6C. It is concluded that the harmattan is thermally more stressful than the hot-dry season and that passive thermolability may not be an important mechanism in the Savanna Brown goat in adaptation to thermal stress. 相似文献
11.
A chimeric stilbene synthase (sts)gene was transferred into wheat. Stilbene synthases play a role in the defence against fungal diseases in some plant species (e.g. groundnut or grapevine) by producing stilbenetype phytoalexins like resveratrol. Resveratrol is also claimed to have positive effects to human health. Embryogenic scutellar calli derived from immature embryos of the two commercial German spring wheat cultivars Combi and Hanno were used as target tissue for cotransformation by microprojectile delivery. The selectable marker/reporter gene constructs contained the bargene either driven by the ubiquitinpromoter from maize (pAHC 25, also containing the uidAgene driven by the ubiquitinpromoter), or by the actinpromoter (pDM 302) from rice. The cotransferred plasmid pStil 2 consisted of a grapevine stscoding region driven by the ubiquitin promoter. Eight transgenic Combi and one Hanno TOplant were obtained and, except one Combi TOplant, found to be cotransformants due to the integration of both the stsgene and the selectable marker or reporter genes. Expression of the stsgene was proven by RTPCR, and, for the first time, by detection of the stilbene synthase product resveratrol by HPLC and mass spectrometry. The stsgene was expressed in four of the seven transgenic Combi T_oplants. Two of the respective T1progenies segregated in a Mendelian manner were still expressing the gene. Investigations into methylation of the stsgene showed that in three nonexpressing progenies inactivation was paralleled by methylation. 相似文献
12.
K. Shimizu 《Biochemical genetics》1987,25(3-4):197-203
DNA polymorphism patterns linked to the A-globin gene were analyzed in healthy Japanese using four different restriction endonucleases. The chromosomes with the A-globin gene were mapped through an evaluation of the presence of seven different restriction sites (HincII 5 to ; HindIII in G and A; HincII in, and 3 to, 1; AvaII in ; Bam-HI 3 to ). Among 36 chromosomes analyzed, 20 chromosomes had a haplotype of [+–––––+]. Among 55 individuals examined, 7 possessed a homozygous haplotye of [+–––––+]. All Japanese with the AT-globin gene had a subhaplotype of [–++–+] 5 to the -globin gene. Their major haplotypes were [–++–+–+] and [–++–++–]. It was expected that the presence of the AT-globin gene in Japanese may be deduced from subhaplotypes 5 to the -globin gene. 相似文献
13.
Prof. Dr. Karl Steinbuch 《Biological cybernetics》1965,2(4):148-152
Summary The performance of the Learning Matrix (LM) is suitable for the design of adaptive networks of higher complexity. It has been published, how to connect a LM with a generator of patterns (binary or nonbinary) and a ring-counter to result in an automatic classification of the presented patterns. This paper describes, how to connect two LM's to form an Autonomous Learning Matrix Dipole (ALD) and how to organize it, so that it adapts itself to an environment according to a given evaluation scale. For this purpose, a third type of input (beside e and b), namely h seems to be useful. This h-input controls the rate of adaptation of the LM.Using such ALD's, one may design adaptive structures of even higher complexity, for example with an adaptive internal model.The principle of Learning Matrices has been explained in detail (see e.g. IEEE Transactions on Electronic Computers, Vol. EC-12, No. 6, December, 1963, pp. 846–862). Using such learning matrices (LM), one may build up adaptive networks with rather interesting functions. Perhaps they are interesting for the physiologist and psychologist as well as for the engineer. Let us first recall the most essential details of the LM's.
Visiting Professor of Electrical Engineering Stanford University. 相似文献
Zusammenfassung Die Funktion der Lernmatrix (LM) erlaubt den Entwurf adaptiver Netzwerke höherer Komplexität. Es wurde an anderer Stelle schon beschrieben, wie eine LM (binär oder nichtbinär) mit einem Generator für Eigenschaftssätze und einem Ringzähler zusammengeschaltet werden kann, um eine selbsttätige Klassifikation der angebotenen Eigenschaftssätze zu bewirken. Im vorliegenden Aufsatz wird erklärt, wie zwei LM so zusammengeschaltet werden können, dacß sich ein Autonomer Lernmatrix-Dipol (ALD) ergibt, und wie dieser zu organisieren ist, daß er sich einer gegebenen Außenwelt nach Maßgabe einer vorgegebenen Werteskala anpaßt. Zu diesem Zweck erweist sich außer den bisher beschriebenen beiden Zugangen zur LM (nämlich e und b) ein dritter sehr zweckmäßig, nämlich h. Dieser h-Eingang beeinflußt die Lerngeschwindigkeit der LM.Unter Verwendung solcher ALD's kann man adaptive Strukturen noch höherer Komplexität aufbauen, beispielsweise solche mit adaptivem innerem Modell.
Visiting Professor of Electrical Engineering Stanford University. 相似文献
14.
George P. Patrinos Aphrodite Loutradi-Anagnostou Manoussos N. Papadakis 《Human genetics》1996,97(3):357-358
A new TA base substitution, identified inside the 5 regulatory region of the humanA globin gene (A –499 T A), is reported. This nucleotide change was found to be linked incis with the mutation producing sickle cell anemia (CD6 GAGGTG: s gene). 相似文献
15.
Summary We have studied the reactions between adenosine 5-phosphorimidazolide and 9-(2-amino-2-deoxyxylofuranosyl) adenine (I) or 3-methylamino-3-deoxyadenosine (II), both with and without a poly (U) template. We find that both amino compounds react much more rapidly than does adenosine, in the absence of a template. The rate of reaction is greatly enhanced by a poly (U) template in the case of I, but the enhancement is slight in the case of II.Abbreviations A
adenosine
- xylo ANH2
9-(2-amino-2-deoxy--D-xylofuranosyl) adenine
- ANHMe
3-methylamino-3-deoxyadenosine
- ImpA
adenosine 5-phosphorimidazolide
- A3 pA
adenylyl-[35]-adenosine
- A2 pA
adenylyl-[25]-adenosine
- UNPA
adenylyl-[52]-2-amino-2-deoxyuridine
- xylo ANPA
9-[adenylyl-(52)-2-amino-2-deoxy--D-xylofuranosyl]adenine
- A(NMe)pA
adenylyl-[53]-3-methylamino-3-deoxyadenosine
- pA
adenosine 5phosphate
- AppA
P1, P2-diadenosine 5pyrophosphate
- (pA)n
n = 2, 3 [2-5]-linked oligomers of pA
- A2 pA2 pA
[2-5]-linked trinucleoside diphosphate of A
- poly (U)
polyuridylic acid 相似文献
16.
Konrad E. Huppi Lawrence A. D'Hoostelaere Beverly A. Mock Evelyne Jouvin-Marchel Mark A. Behlke Hubert S. Chou R. J. Berry Dennis Y. Loh 《Immunogenetics》1988,27(1):51-56
The composition of 15 V
T gene subfamilies has been examined by Southern hybridization among a broad spectrum of colony bred rat and mouse species extending phylogenetically from Rattus to Mus musculus domesticus. Most mouse species contain a similar content of V
T genes as determined by the number of hybridizing restriction fragment (RF) bands. Furthermore, the extent of restriction fragment length polymorphism (RFLP) appears to be limited. Some V
T gene families, however, are missing from Rattus (VT7, V
T12) and M. shortridgei (V
T9, V
T16). Extension of the V
T survey to a panel of 38 wild-caught mice reveals that nearly a third lack specific hybridization to the V
T5 probe. Previous reports have established that the mouse inbred strains SJL, C57BR, C57L, and SWR lack 50% of their V
T repertoire, including V
T5 (Behlke et al. 1985). This study demonstrates that natural populations of mice also carry a significantly reduced V
T gene repertoire. 相似文献
17.
The respiratory chain of a marine bacterium,Vibrio alginolyticus, required Na+ for maximum activity, and the site of Na+-dependent activation was localized on the NADH-quinone reductase segment. The Na+-dependent NADH-quinone reductase extruded Na+ as a direct result of redox reaction. It was composed of three subunits, , , and , with apparentMr of 52, 46, and 32 KDa, respectively. The reduction of ubiquinone-1 to ubiquinol proceeded via ubisemiquinone radicals. The former reaction was catalyzed by the FAD-containing subunit. This reaction showed no specific requirement for Na+. For the formation of ubiquinol, the presence of the subunit and the FMN-containing subunit was essential. The latter reaction specifically required Na+ for activity and was strongly inhibited by 2-n-heptyl-4-hydroxyquinolineN-oxide. It was assigned to the coupling site for Na+ transport. The mode of energy coupling of redox-driven Na+ pump was compared with those of decarboxylase- and ATP-driven Na+ pumps found in other bacteria. 相似文献
18.
Dudy Bar-Zvi Masasuke Yoshida Noun Shavit 《Journal of bioenergetics and biomembranes》1996,28(6):471-481
Photoaffinity labeling by 3-O-(4-benzoyl)benzoyl adenosine 5-triphosphate (BzATP) of the adenine nucleotide binding site(s) on isolated and complexed and subunits of F1-ATPase from the thermophilic bacterium PS3 (TF1) is described. BzATP binds to both isolated and subunits, to complexed subunit but not to complexed subunit. Amino acid sequence determination of radiolabeled peptides obtained by proteolytic digestion of [-32P]BzATP-labeled subunit indicates that residues on both the amino-terminal (residues A41-E67) and carboxy-terminal (residues Q422–Q476) were modified by BzATP. One of the residues in the carboxy-terminal modified by BzATP is most probably Q422. Although the binding stoichiometry of 1 mol of BzATP incorporated by either isolated or complexed subunit was maintained, the spatial conformation of the polypeptide determines which amino acid residue(s) is more accessible to the reactive radical. CNBr derived fragments G10-M64, E75-M233, and D390-M469 were labeled with the isolated subunit. With complexed subunit the label was found only in CNBr fragments: E75-M233 and G339-M389. The locations where the covalently bound BzATP was found, in the soluble and assembled subunits, indicate that different conformational states exist. In the isolated form of the and subunits the amino- and carboxy-termini can fold and reach the central domain of the polypeptide, the domain containing the adenine nucleotide binding site. When combines with to form the 33 core complex the new conformation of the subunits is such that covalent labeling by BzATP of and of the amino terminal of subunit is excluded. 相似文献
19.
F. Ordon W. Friedt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(2-3):229-233
Summary In order to obtain information about the mode of inheritance of BaMMV resistance in germplasms carrying genes different from the German gene ym4 f1-tests for resistance as well as F2-segregation analyses of crosses to susceptible German cultivars were carried out by mechanical inoculation in the greenhouse. In the f1 the majority of plants of each combination tested reacted susceptible to BaMMV while in the F2 a good fit to a segregation of 1r:3s or 7r:9s was observed. Therefore, the results of these tests revealed that the BaMMV resistance of all the varieties tested is inherited either by a single or by two recessive genes. By testing intercrosses of these resistant varieties segregation of BaMMV-susceptile plants was observed in the majority of combinations, revealing a high degree of genetic diversity in the barley gene pool.Dedicated to Professor Dr. Wolfgang Schnell on the occasion of his 80th birthday 相似文献
20.
The catalytic transition state of ATP synthase has been characterized and modeled by combined use of (1) Mg-ADP–fluoroaluminate, Mg-ADP–fluoroscandium, and corresponding Mg-IDP–fluorometals as transition-state analogs; (2) fluorescence signals of -Trp331 and -Trp148 as optical probes to assess formation of the transition state; (3) mutations of critical catalytic residues to determine side-chain ligands required to stabilize the transition state. Rate acceleration by positive catalytic site cooperativity is explained as due to mobility of -Arg376, acting as an arginine finger residue, which interacts with nucleotide specifically at the transition state step of catalysis, not with Mg-ATP- or Mg-ADP-bound ground states. We speculate that formation and collapse of the transition state may engender catalytic site / subunit-interface conformational movement, which is linked to -subunit rotation. 相似文献