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21.
Role of poly(A) polymerase in the cleavage and polyadenylation of mRNA precursor. 总被引:10,自引:5,他引:5
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To determine the role of poly(A) polymerase in 3'-end processing of mRNA, the effect of purified poly(A) polymerase antibodies on endonucleolytic cleavage and polyadenylation was studied in HeLa nuclear extracts, using adenovirus L3 pre-mRNA as the substrate. Both Mg2+- and Mn2+-dependent reactions catalyzing addition of 200 to 250 and 400 to 800 adenylic acid residues, respectively, were inhibited by the antibodies, which suggested that the two reactions were catalyzed by the same enzyme. Anti-poly(A) polymerase antibodies also inhibited the cleavage reaction when the reaction was coupled or chemically uncoupled with polyadenylation. These antibodies also prevented formation of specific complexes between the RNA substrate and components of nuclear extracts during cleavage or polyadenylation, with the concurrent appearance of another, antibody-specific complex. These studies demonstrate that (i) previously characterized poly(A) polymerase is the enzyme responsible for addition of the poly(A) tract at the correct cleavage site and probably for the elongation of poly(A) chains and (ii) the coupling of these two 3'-end processing reactions appears to result from the potential requirement of poly(A) polymerase for the cleavage reaction. The results suggest that the specific endonuclease is associated with poly(A) polymerase in a functional complex. 相似文献
22.
Shi Liu Ron Jacob David Piwnica-Worms Melvyn Lieberman 《Molecular and cellular biochemistry》1989,89(2):147-150
We have recently reported the presence of an electroneutral (Na + K + 2 Cl) cotransport mechanism that is bumetanide-sensitive and maintains Cli above its electrochemical equilibrium in cultured chick heart cells. In steady state, (Na + K + 2 Cl) cotransport is inwardly directed and so contributes to the Na influx that must be counterbalanced by the activity of the Na/K pump to maintain Nai homeostasis. We now show that manipulating (Na + K + 2 Cl) cotransport by restoring Clo to a Cl-free solution indirectly influences Na/K pump activity because the bumetanide-sensitive recovery of a
infNa
supi
to its control level and the accompanying hyperpolarization could be blocked by 10–4M ouabain. In another protocol, when the Na/K pump was reactivated by restoring Ko (from 0.5 mM to 5.4 mM) and removing ouabain, the recovery of aNa was attenuated by 10–4M bumetanide. The relatively slow rate of ouabain dissociation coupled with the activation of Na influx by (Na + K + 2 Cl) cotransport clearly establishes the interaction of these transport mechanisms in regulating Nai. Although (Na + K + 2 Cl) cotransport is electroneutral, secondary consequences of its activity can indirectly affect the electrophysiological properties of cardiac cells. 相似文献
23.
Effects of Prechilling and Sequential Washing on Enumeration of Microorganisms from Refuse 总被引:1,自引:1,他引:0
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Techniques were evaluated for formation of a liquid inoculum from shredded municipal refuse, including chilling the refuse at 4°C prior to blending and multiple washing and blending cycles. The average count of cellulolytic bacteria from six different detachment treatments was 5.1 × 104 cells per g (dry weight) of refuse with a range of 0.7 × 104 to 12.7 × 104 cells per g (dry weight). The liquid obtained from blending the refuse in phosphate buffer followed by hand squeezing was the selected detachment procedure. The inoculum formation procedure was validated by the addition of ruminal cellulolytic bacteria to refuse and recovery of the cellulolytic bacteria by most-probable-number enumerations. The ratio of measured to expected cell counts among tests in which different volumes of ruminal fluid were added to refuse ranged from 2.7 to 14.4. There was no evidence of anaerobic cellulolytic fungi in a refuse sample. 相似文献
24.
25.
The partial collapse of dipolar and chemical shift tensors for peptide NH and for the amide NH at cross-link sites in cell wall peptidoglycan, of intact lyophilized cells of Aerococcus viridans, indicates NH vector root-mean-square fluctuations of 23 degrees. This result is consistent with the local mobility calculated in typical picosecond regime computer simulations of protein dynamics in the solid state. The experimental root-mean-square angular fluctuations for both types of NH vectors increase to 37 degrees for viable wet cells at 10 degrees C. The similarity in mobilities for both general protein and cell wall peptidoglycan suggests that one additional motion in wet cells involves cooperative fluctuations of segments of cell walls, attached proteins, and associated cytoplasmic proteins. 相似文献
26.
27.
Characterization of the cDNA coding for mouse plasminogen and localization of the gene to mouse chromosome 17 总被引:4,自引:0,他引:4
A full-length cDNA coding for mouse plasminogen has been isolated and characterized. The cDNA is 2720 bp in length (excluding the poly(A) tail) and contains a 24-bp 5' noncoding region, an open reading frame of 2436 bp, and a 3' noncoding region of 257 bp. The open reading frame codes for 812 amino acids and includes a signal peptide that is likely 19 amino acids in length and the mature protein of 793 amino acids. The calculated Mr of mouse plasminogen is 88,706 excluding carbohydrate. There are two potential N-linked carbohydrate addition sites; one of which is glycosylated in human, bovine, and porcine plasminogens. Mouse plasminogen was found to contain two additional amino acids compared to the human protein. In addition, mouse and human plasminogens were found to be 79 and 76% identical at the protein and DNA levels, respectively. Analysis of the segregation of two allelic forms, Plgb and Plgd, of plasminogen DNA in three sets of recombinant inbred strains has allowed the localization of the mouse plasminogen gene to the proximal end of mouse chromosome 17 within the t complex and close to the locus D17Rp17. The Plg gene is deleted in the semidominant deletion mutant, hair-pintail (Thp). 相似文献
28.
29.
Jose Jacob 《Molecular and cellular biochemistry》1988,84(1):97-103
Summary Effects of Ca2+ ionophores, A23187 and lasalocid, on superoxide anion generation by chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine methyl ester, in rabbit peritoneal exudate neutrophils were studied. The ionophores by themselves did not activate superoxide anion generation in these neutrophils. When preincubated with the cells for 2 min, both the ionophores inhibited superoxide generation induced by chemotactic peptide. The inhibition was present even in the absence of extracellular Ca2+ and the inhibition was better then. Lasalocid produces a dose-dependent chlortetracycline fluorescence decrease response in neutrophils loaded with chlortetracycline. This response is independent of extracellular Ca2+ concentration and is related to release of Ca2+ from intracellular storage sites. The dose-range at which lasalocid gives this response is same as the dose-range at which it causes inhibition of superoxide response. It may be concluded that the inhibition of superoxide generation by these ionophores is correlated to intracellular Ca2+ modulation.Abbreviations FMLP
Formyl-Methionyl-Leucyl-Phenylalanine methyl ester 相似文献
30.
Vered Barenholz-Paniry Jacob S. Ishay Zvi Grossman 《Bulletin of mathematical biology》1988,50(6):661-679
Rhythmic “circa-second” contrations of larvae of the hornetVespa orientalis, believed to serve as hunger signals, were studied. A considerable degree of coordination among individual larvae, both in
frequency and phase of these contractions, has been observed. The oscillations of singly isolated larvae are of short duration,
non-constant, with increasing intervals in between and there is a substantial variability in the patterns shown by different
larvae. In contrast, the association of two or more larvae leads to enhancement of their periodic behaviour and to (partial)
entrainment. Communication among larvae may perhaps be mediated by the sound pulses (“scratching” noises) which are generated
by these contractions. We have subjected individual and grouped larvae to external sound pulses and were able to demonstrate:
(a) enhancement of rhythmic activity; (b) phase resetting; (c) entrainment to an external oscillator within a range of frequencies;
(d) the existence of a subharmonic mode of entrainment. We propose a simple phenomenologic model to account for these larvae
responses. Our model assumes the existence of an “energy” variable which declines with time but is upgraded, in a phase-dependent
way, by external stimuli.
Based in part on work performed by V. Barenholz-Paniry in partial fulfillment of the requirements for the M.Sc. degree from
the Sackler Faculty of Medicine, Tel Aviv University, 1986. 相似文献