Live Chat
Today's Hours: 8:00am - 10:00pm
Lane Medical Library

Search

Filter Applied Clear All

Filter Results

Did You Mean:

Search Results

Sort by
relevance
  • Article
    Melick CH, Meng D, Jewell JL.
    J Biol Chem. 2020 06 05;295(23):8096-8105.
    mTOR complex 1 (mTORC1) senses nutrients to mediate anabolic processes within the cell. Exactly how mTORC1 promotes cell growth remains unclear. Here, we identified a novel mTORC1-interacting protein called protein kinase A anchoring protein 8L (AKAP8L). Using biochemical assays, we found that the N-terminal region of AKAP8L binds to mTORC1 in the cytoplasm. Importantly, loss of AKAP8L decreased mTORC1-mediated processes such as translation, cell growth, and cell proliferation. AKAPs anchor protein kinase A (PKA) through PKA regulatory subunits, and we show that AKAP8L can anchor PKA through regulatory subunit Iα. Reintroducing full-length AKAP8L into cells restored mTORC1-regulated processes, whereas reintroduction of AKAP8L missing the N-terminal region that confers the interaction with mTORC1 did not. Our results suggest a multifaceted role for AKAPs in the cell. We conclude that mTORC1 appears to regulate cell growth, perhaps in part through AKAP8L.
    Digital Access Access Options
  • Article
    Lindsley JE, Wang JC.
    J Biol Chem. 1993 Apr 15;268(11):8096-104.
    The initial rates of ATP hydrolysis and relaxation of negatively supercoiled DNA by highly purified wild-type and mutant yeast DNA topoisomerase II were measured under identical conditions to study the coupling between the ATPase activity of a type II DNA topoisomerase and its catalysis of the transport of one DNA segment through another. The results indicate that the binding of the enzyme to DNA stimulates its intrinsic ATPase activity by about 20-fold, and ATP binding to the pair of ATPase sites in a DNA-bound dimeric enzyme appears to be cooperative. The cooperativity in ATP binding may be significant in the coordination of the two halves of a DNA-bound enzyme dimer. At low ATP concentrations, the rate-limiting step in ATP usage appears to be slower than that in DNA transport, and DNA transport is relatively efficient in terms of ATP consumption: 1.9 +/- 0.5 ATP molecules are hydrolyzed/DNA transport event. At a saturating ATP concentration, however, there appears to be a reversal of these rate-limiting steps, and DNA transport is less efficient: 7.4 +/- 1.0 ATP molecules are hydrolyzed/DNA transport event. These data are interpreted in terms of a model in which a DNA-bound enzyme acts as an ATP-operated clamp for the capture and transport of a second DNA segment.
    Digital Access Access Options
  • Article
    Mandal K, Chakrabarti B, Thomson J, Siezen RJ.
    J Biol Chem. 1987 Jun 15;262(17):8096-102.
    The denaturation behavior of bovine lens gamma-crystallin fractions II, III, and IV and their susceptibility to proteolysis in vitro was compared to determine whether differences in their stability could play a role in cataract formation. Tertiary and secondary structure changes induced by increasing concentrations of urea, guanidine hydrochloride, and sodium dodecyl sulfate and by increasingly alkaline pH were followed by near-UV and far-UV circular dichroism, Trp fluorescence emission, and exposure of sulfhydryl groups. Major differences were found in the denaturation and proteolysis behavior of the three gamma-crystallin fractions. In general, the unfolding of gamma-II and gamma-III crystallins is rather gradual, suggesting the presence of intermediate unfolding states; in contrast, the order-disorder transition of gamma-IV crystallin is abrupt. The gamma-IV crystallin fraction is the most stable in urea and guanidine hydrochloride, but is most susceptible to nonspecific proteolysis and alkaline pH denaturation. Differences in denaturation and proteolysis behavior are attributed to the inherent differences in the tertiary structures of these crystallins.
    Digital Access Access Options
  • Article
    Klionsky DJ, Skalnik DG, Simoni RD.
    J Biol Chem. 1986 Jun 25;261(18):8096-9.
    Translation of the gene for the b subunit of the Escherichia coli proton-translocating ATPase has been examined. Oligonucleotide-directed site-specific mutagenesis was used to mutate certain nucleotides in the intergenic region between uncE (c) and uncF (b). One of the changes was predicted to lower the stability of a proposed stem structure which blocked the ribosome binding site of the uncF mRNA segment. The result of the mutation is a nearly 3-fold increase in the rate of synthesis of the b polypeptide. Another mutation was introduced which changed the initiation codon for uncF from GUG to AUG. This change resulted in an approximately 2-fold increase in the synthesis rate of the b polypeptide. These results suggest that secondary structure in the mRNA and the use of a less efficient initiation codon play a role in restricting translation initiation of the uncF mRNA segment. These mechanisms may, in part, explain how the polypeptides of the ATPase complex are synthesized in approximately the same relative amounts as they appear in the assembled complex.
    Digital Access Access Options
  • Article
    Sakahira H, Iwamatsu A, Nagata S.
    J Biol Chem. 2000 Mar 17;275(11):8091-6.
    Caspase-activated DNase (CAD) is the enzyme that causes DNA fragmentation during apoptosis. CAD forms aggregates when it is synthesized in the absence of an inhibitor of CAD (ICAD). Here, using renaturation systems of chemically denatured CAD, we report that ICAD-L, a long form of ICAD, has a chaperone-like activity specific for CAD. Murine CAD carries 14 cysteines, most of which were found to be in reduced form. Reducing agents enhanced the production of the functional CAD in an in vitro translation system. The denatured CAD could be efficiently renatured under highly reducing conditions only in the presence of ICAD-L. This process was ATP-independent. In contrast, reticulocyte lysates stimulated ICAD-L- and ATP-dependent renaturation of denatured CAD without requiring a high concentration of reducing agents. These results indicate that ICAD-L works not only as a specific inhibitor but also as a specific chaperone for CAD.
    Digital Access Access Options
  • Article
    Moy JA, Bates JN, Fisher RA.
    J Biol Chem. 1991 May 05;266(13):8092-6.
    Effects of nitric oxide (NO) on hemodynamic and glycogenolytic responses to platelet-activating factor (PAF) and phenylephrine were investigated in perfused livers derived from fed rats. Infusion of NO (34 microM) into perfused livers inhibited PAF (0.22 nM)-induced increases in hepatic glucose output and portal pressure approximately 90 and 85%, respectively, and abolished effects of PAF on hepatic oxygen consumption. NO attenuated PAF-stimulated increases in glucose output and portal pressure, the latter indicative of hepatic vasoconstriction, with a similar dose dependence with an IC50 of approximately 8 microM. In contrast to its effects on PAF-induced responses in the perfused liver, NO inhibited increases in hepatic portal pressure in response to phenylephrine (10 microM) approximately 75% without altering phenylephrine-stimulated glucose output and oxygen consumption. Similarly, infusion of NO into perfused livers significantly inhibited increases in hepatic portal pressure but not in glucose output in response to a submaximal concentration of phenylephrine (0.4 microM). Like NO, sodium nitroprusside (83 microM) significantly inhibited hemodynamic but not glycogenolytic responses to phenylephrine in perfused livers. However, PAF (0.22 nM)-stimulated alterations in hepatic portal pressure, glucose output, and oxygen consumption were unaffected by infusion of sodium nitroprusside (83 microM) into perfused livers. These results provide the first evidence for regulatory effects of NO in the perfused liver and support the contention that PAF, unlike phenylephrine, stimulates glycogenolysis by mechanisms secondary to hepatic vasoconstriction. These observations raise the intriguing possibility that NO may act in liver to regulate hemodynamic responses to vasoactive mediators.
    Digital Access Access Options
  • Article
    Lynch JB, Juarez-Garcia C, Münck E, Que L.
    J Biol Chem. 1989 May 15;264(14):8091-6.
    57Fe-enriched ribonucleotide reductase subunit B2 from Escherichia coli strain N6405/pSPS2 has been characterized by Mössbauer and EPR spectroscopy in its native diferric state and in a new differous form. The native protein exhibits two Mössbauer doublets in a 1:1 ratio with parameters that are in excellent agreement with those reported for the wild-type protein (Atkin, C. L., Thelander, L., Reichard, P., and Lang, G. (1983) J. Biol. Chem. 248, 7464-7472); in addition, our studies show the absence of adventitiously bound iron. The iron content in the present samples approached 4 per B2 subunit, and the tyrosyl radical content exceeded 1 per B2 subunit. The higher values are attributed to the use of a new epsilon 280 for the protein and more efficient methods for iron extraction. We thus propose that subunit B2 has two binuclear iron clusters, each associated with its own tyrosyl radical, in contradistinction from the prevailing model. Reduction of the native protein with dithionite or reconstitution of the apoprotein with Fe(II) afforded a protein complex with Mössbauer parameters, delta EQ = 3.13 mm/s and delta = 1.26 mm/s at 4.2 K, and a low field EPR signal associated with an integer spin system. These spectral properties resemble those of methane monooxygenase in its diferrous form. Upon exposure to O2, the reduced subunit B2 readily converts to the diferric state and yields active enzyme.
    Digital Access Access Options
  • Article
    Otsu K, Kinsella JL, Koh E, Froehlich JP.
    J Biol Chem. 1992 Apr 25;267(12):8089-96.
    The pre-steady state time dependence of Na+ accumulation by the Na(+)-H+ exchanger in renal brush border membrane vesicles was investigated at 0 degree C by a manual mixing technique using amiloride to quench the reaction. Dilution of acid-loaded (pHi 5.7) vesicles into an alkaline medium (pHo 7.7) containing 1 mM 22Na+ produced a time course of amiloride-sensitive Na+ uptake that consisted of three distinct phases: 1) a lag, 2) a monoexponential "burst," and 3) a linear or steady state phase. Experiments testing for the presence of 22Na+ backflux, residual Na+ binding to the membrane, and hysteresis were negative, lending support to the hypothesis that the burst phase corresponds to Na+ translocation during the initial turnover of Na(+)-H+ exchanger. Lowering the internal pH increased the amount of na+ uptake in each of the phases without affecting the apparent burst rate, whereas lowering the external pH inhibited Na+ uptake while increasing the duration of the lag phase. The pattern of inhibition produced by external H+ was of the simple competitive type, indicating that Na+ and H+ share a common binding site. Steady state Na+ uptake showed a sigmoidal dependence on internal pH (Hill coefficient = 1.67), consistent with the presence of an internal allosteric H+ activation site. Alkaline loading conditions (pHi 7.7), which favor desaturation of the internal H+ binding sites, completely abolished Na+ uptake in the steady state. In contrast, Na+ accumulation during the burst phase was reduced to 25% of an acid-loaded (pHi 5.7) control. The persistence of the burst phase and the disappearance of steady state Na+ uptake under alkaline loading conditions suggest that recycling of the H(+)-loaded exchanger is a late event in the transport cycle that follows Na+ translocation (ping-pong mechanism) and controls the steady state rate of Na+ accumulation. Activation of the recycling step involves sequential binding of H+ to the allosteric and transport sites, thus accounting for the cooperative dependence of steady state Na+ uptake on the internal [H+].
    Digital Access Access Options
  • Article
    Buse MG, Biggers JF, Friderici KH, Buse JF.
    J Biol Chem. 1972 Dec 25;247(24):8085-96.
    Digital Access Access Options