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111.
112.
Primary structure of the deoxyguanosine triphosphate triphosphohydrolase-encoding gene (dgt) of Escherichia coli 总被引:1,自引:0,他引:1
The complete nucleotide sequence has been determined for a 2027-bp region that encompasses the structural gene (dgt) encoding deoxyguanosine triphosphate triphosphohydrolase (dGTPase) from Escherichia coli. The gene resides between the htrA and dapD loci at 3.75-3.8' on the bacterial chromosome. Using homologous recombination in a recD recipient, a dgt- bacterial strain was constructed that was deficient in producing functional dGTPase. Comparison of dGTP pools in this and other strains revealed that dGTPase synthesized in vivo does to some degree modulate the level of dGTP in the bacterial cell, yet the magnitude of this modulation may be insufficient to explain the physiological function of dGTPase. 相似文献
113.
114.
R Z Hawirko P K Bhatnagar K L Chung C T Chow 《Canadian journal of microbiology》1977,23(12):1706-1713
The effect of rifampicin on the developmental phases of germinating spores of Clostridium botulinum, MSp+, has been studied. At sublethal concentrations of rifampicin (0.05 ng/ml) the time periods required for outgrowth and vegetative growth was significantly prolonged because of the inhibition of RNA and protein synthesis. However, rifampicin had essentially no effect on DNA synthesis or on subsequent spore formation. Chemical analyses showed that the amount of protein present in vegetative cells of the rifampicin-treated cultures was twice as great as in the untreated cultures but the total protein content of endospores was the same in both cases. It was revealed in ultrastructural studies of rifampicin (0.1 ng/ml) treated cultures, examined after 22 h, that septum formation and normal cell division of the emerging cell was blocked and a few cells showed constriction which produced one normal and one protoplast-like daughter cell. 相似文献
115.
Background
The development of effective environmental shotgun sequence binning methods remains an ongoing challenge in algorithmic analysis of metagenomic data. While previous methods have focused primarily on supervised learning involving extrinsic data, a first-principles statistical model combined with a self-training fitting method has not yet been developed. 相似文献116.
117.
The mutT protein, which prevents A:T----C:G transversions during DNA replication, has the following enzymatic properties. Although it prefers dGTP as a substrate, it hydrolyzes all of the canonical nucleoside triphosphates to some extent. It has no activity in the absence of divalent cations, is maximally activated by magnesium ions, and has a pH optimum of 9.0. Nucleoside triphosphates are hydrolyzed according to the following equation. dGTP----dGMP + PPi Studies with nucleotide analogues suggest that the enzyme may prefer the syn rather than the anti conformation of the nucleoside triphosphates, which might explain the role it plays in preventing mutations. 相似文献
118.
Luminita Göbbel Martin S. Fischer Timothy D. Smith John R. Wible Kunwar P. Bhatnagar 《Acta zoologica》2004,85(1):41-52
The vomeronasal organ (VNO) is a chemosensory structure of the nasal septum found in most tetrapods. Although potential behavioural correlates of VNO function have been shown in two of the three elephant species, its morphology in Loxodonta africana has not been studied. The development of the VNO and its associated structures in the African elephant are described in detail using serially sectioned material from fetal stages. The results show that many components of the VNO complex (e.g. neuroepithelium, receptor‐free epithelium, vomeronasal nerve, paravomeronasal ganglia, blood vessels, vomeronasal cartilage) are well developed even in a 154‐day‐old fetus, in which the VNO opens directly into the oral cavity with only a minute duct present. However, the vomeronasal glands and their ducts associated with the VNO were developed only in the 210‐day‐old fetus. Notably, in this fetus, the vomeronasal–nasopalatine duct system had acquired a pathway similar to that described in the adult Asian elephant; the VNOs open into the oral cavity via the large palatal parts of the nasopalatine ducts, which are lined by a stratified squamous epithelium. The paired palatal ducts initially coursed anteriorly at an angle of 45° from the oral recess and/or the oral cavity mucosa, and merged into the vomeronasal duct. This study confirms the unique characteristics of the elephant VNO, such as its large size, the folded epithelium of the VNO tube, and the dorsomedial position of the neuroepithelium. The palatal position and exclusive communication of the VNO with the oral cavity, as well as the partial reduction of the nasopalatine duct, might be related to the unique elephantid craniofacial morphogenesis, especially the enormous growth of the tusk region, and can be seen as autapomorphies. 相似文献
119.
A deltamethrin containing insecticide formulation (Decis®) was evaluated for its toxic potential in developing chick embryos. For the present study, three water emulsified concentrations of Decis® (12.5 mg L?1, 25 mg L?1, and 50 mg L?1) were used. Fertilized eggs of Gallus domesticus were immersed in these three concentrations of the insecticide for 60 min at 37°C on day 0 of incubation and kept for incubation till embryonic day 7. Recovered embryos were evaluated for teratogenic and biochemical changes. The results revealed that administration of Decis® at its lower concentrations (12.5 mg L?1 and 25 mg L?1) did not show any significant teratological changes but the significant number of abnormal survivors was observed at 50 mg L?1 of dose concentration when compared with vehicle-treated control. Among biochemical changes, total glycogen and RNA contents of embryos was significantly decreased at 25 mg L?1 and 50 mg L?1 of Decis® concentrations. Similarly, significant alteration (p ≤ .05) was observed in alanine transaminase activity at 50 mg L?1 concentration of Decis®. Thus, the present study concluded that the no-effect-level for developmental toxicity for Decis® is below the concentration of 25 mg L?1 under standard laboratory conditions. 相似文献
120.
Tipparaju SM Liu SQ Barski OA Bhatnagar A 《Biochemical and biophysical research communications》2007,359(2):269-276
Ancillary beta-subunits regulate the voltage-dependence and the kinetics of Kv currents. The Kvbeta proteins bind pyridine nucleotides with high affinity but the role of cofactor binding in regulating Kv currents remains unclear. We found that recombinant rat Kvbeta 1.3 binds NADPH (K(d)=1.8+/-0.02 microM) and NADP(+) (K(d)=5.5+/-0.9 microM). Site-specific modifications at Tyr-307 and Arg-316 decreased NADPH binding; whereas, K(d) NADPH was unaffected by the R241L mutation. COS-7 cells transfected with Kv1.5 cDNA displayed non-inactivating currents. Co-transfection with Kvbeta1.3 accelerated Kv activation and inactivation and induced a hyperpolarizing shift in voltage-dependence of activation. Kvbeta-mediated inactivation of Kv currents was prevented by the Y307F and R316E mutations but not by the R241L substitution. Additionally, the R316E mutation weakened Kvalpha-beta interaction. Inactivation of Kv currents by Kvbeta:R316E was restored when excess NADPH was included in the patch pipette. These observations suggest that NADPH binding is essential for optimal interaction between Kvalpha and beta subunits and for Kvbeta-induced inactivation of Kv currents. 相似文献