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Proceedings of the National Academy of Sciences of... 110건

  1. [해외논문]   Myosin light-chain kinase of smooth muscle stimulates myosin ATPase activity without phosphorylating myosin light chain.  

    Ye, L H , Kishi, H , Nakamura, A , Okagaki, T , Tanaka, T , Oiwa, K , Kohama, K
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6666 - 6671 , 1999 , 0027-8424 ,

    초록

    Myosin light-chain kinase (MLCK) of smooth muscle is multifunctional, being composed of N-terminal actin-binding domain, central kinase domain, and C-terminal myosin-binding domain. The kinase domain is the best characterized; this domain activates the interaction of smooth-muscle myosin with actin by phosphorylating the myosin light chain. We have recently shown that the Met-1-Pro-41 sequence of MLCK binds to actin to inhibit this interaction. However, it is not known whether the myosin-binding domain modifies the actin-myosin interaction. We designed MLCK.cDNA to overexpress the Asp-777-Glu-972 sequence in Escherichia coli. The purified Asp-777-Glu-972 fragment, although devoid of the kinase activity, exerted a stimulatory effect on the ATPase activity of dephosphorylated myosin (Vmax = 7.36 +/- 0.44-fold, Km = 1.06 +/- 0. 20 microM, n = 4). When the N-terminal 39 residues of the fragment were deleted from the fragment, the resultant fragment, Met-816-Glu-972, lost the stimulatory activity. We synthesized the Ala-777-Ser-815 peptide that was deleted from the fragment and confirmed its stimulatory effect of the peptide (Vmax = 3.03 +/- 0. 22-fold, Km = 6.93 +/- 1.61 microM, n = 3). When this peptide was further divided into Asp-777-Met-795 and Ala-796-Ser-815 peptides, the stimulatory activity was found in the latter. We confirmed that the myosin phosphorylation did not occur during the experiments with the above fragments and peptides. Therefore, we suggest that phosphorylation is not obligatory for smooth-muscle myosin not to be active.

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  2. [해외논문]   Substrate binding and catalysis by ribonuclease P from cyanobacteria and Escherichia coli are affected differently by the 3' terminal CCA in tRNA precursors.  

    Pascual, A , Vioque, A
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6672 - 6677 , 1999 , 0027-8424 ,

    초록

    We have studied the effect of the 3' terminal CCA sequence in precursors of tRNAs on catalysis by the RNase P RNA or the holoenzyme from the cyanobacterium Synechocystis sp. PCC 6803 in a completely homologous system. We have found that the absence of the 3' terminal CCA is not detrimental to activity, which is in sharp contrast to what is known in other bacterial systems. We have found that this is also true in other cyanobacteria. This situation correlates with the anomalous structure of the J15/16 loop in cyanobacteria, which is an important loop in the CCA interaction in Escherichia coli RNase P, and with the fact that cyanobacteria do not code the CCA sequence in the genome but add it posttranscriptionally. Modification of nucleotides 330-332 in the J15/16 loop of Synechocystis RNase P RNA from GGU to CCA has a modest effect on kcat for CCA-containing substrates and has no effect on cleavage-site selection. We have developed a direct physical assay of the interaction between RNase P RNA and its substrate, which was immobilized on a filter, and we have determined that Synechocystis RNase P RNA binds with better affinity the substrate lacking CCA than the substrate containing it. Our results indicate a mode of substrate binding in RNase P from cyanobacteria that is different from binding in other eubacteria and in which the 3' terminal CCA is not involved.

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  3. [해외논문]   Lon and Clp family proteases and chaperones share homologous substrate-recognition domains.  

    Smith, C K , Baker, T A , Sauer, R T
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6678 - 6682 , 1999 , 0027-8424 ,

    초록

    Lon protease and members of the Clp family of molecular chaperones and protease regulatory subunits contain homologous regions with properties expected for substrate-binding domains. Fragments corresponding to these sequences are stably and independently folded for Lon, ClpA, and ClpY. The corresponding regions from ClpB and ClpX are unstable. All five fragments exhibit distinct patterns of binding to three proteins that are protease substrates in vivo: the heat shock transcription factor sigma32, the SOS mutagenesis protein UmuD, and Arc repressor bearing the SsrA degradation tag. Recognition of UmuD is mediated through peptide sequences within a 24-residue N-terminal region whereas recognition of both sigma32 and SsrA-tagged Arc requires sequences at the C terminus. These results indicate that the Lon and Clp proteases use the same mechanism of substrate discrimination and suggest that these related ATP-dependent bacterial proteases scrutinize accessible or disordered regions of potential substrates for the presence of specific targeting sequences.

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  4. [해외논문]   ZEB represses transcription through interaction with the corepressor CtBP.  

    Postigo, A A , Dean, D C
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6683 - 6688 , 1999 , 0027-8424 ,

    초록

    ZEB is an active transcriptional repressor that regulates lymphocyte and muscle differentiation in vertebrates. Its homologue in Drosophila (zfh-1) is also essential for differentiation of somatic and cardiac muscle. Here, we demonstrate that ZEB and zfh-1 interact with the corepressor CtBP to repress transcription. ZEB and zfh-1, both contain the sequence PLDLS in the same region of the repressor domain, and we demonstrate that this sequence binds CtBP-1 and -2. In vertebrate species, ZEB contains two additional CtBP-like binding sites (variations of the PLDLS sequence) that also bind CtBP proteins and are required for full repressor activity. The three sites have an additive effect, and mutation of all three sites is necessary to abolish both binding to CtBP and repressor activity. Finally, we demonstrate that the interaction of CtBP with ZEB at the promoter is necessary for repressor activity.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  5. [해외논문]   Declines in mitochondrial respiration during cardiac reperfusion: Age-dependent inactivation of -ketoglutarate dehydrogenase  

    Lucas, D. T. , Szweda, L. I.
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6689 - 6693 , 1999 , 0027-8424 ,

    초록

    ZEB is an active transcriptional repressor that regulates lymphocyte and muscle differentiation in vertebrates. Its homologue in Drosophila (zfh-1) is also essential for differentiation of somatic and cardiac muscle. Here, we demonstrate that ZEB and zfh-1 interact with the corepressor CtBP to repress transcription. ZEB and zfh-1, both contain the sequence PLDLS in the same region of the repressor domain, and we demonstrate that this sequence binds CtBP-1 and -2. In vertebrate species, ZEB contains two additional CtBP-like binding sites (variations of the PLDLS sequence) that also bind CtBP proteins and are required for full repressor activity. The three sites have an additive effect, and mutation of all three sites is necessary to abolish both binding to CtBP and repressor activity. Finally, we demonstrate that the interaction of CtBP with ZEB at the promoter is necessary for repressor activity.

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  6. [해외논문]   Declines in mitochondrial respiration during cardiac reperfusion: age-dependent inactivation of alpha-ketoglutarate dehydrogenase.  

    Lucas, D T , Szweda, L I
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6689 - 6693 , 1999 , 0027-8424 ,

    초록

    We previously reported that cardiac reperfusion results in declines in mitochondrial NADH-linked respiration. The degree of inactivation increased with age and was paralleled by modification of protein by the lipid peroxidation product 4-hydroxy-2-nonenal. To gain insight into potential sites of oxidative damage, the present study was undertaken to identify specific mitochondrial protein(s) inactivated during ischemia and reperfusion and to determine which of these losses in activity are responsible for observed declines in mitochondrial respiration. Using a Langendorff rat heart perfusion protocol, we observed age-dependent inactivation of complex I during ischemia and complex IV and alpha-ketoglutarate dehydrogenase during reperfusion. Although losses in complex I and IV activities were found not to be of sufficient magnitude to cause declines in mitochondrial respiration, an age-related decrease in complex I activity during ischemia may predispose old animals to more severe oxidative damage during reperfusion. It was determined that inactivation of alpha-ketoglutarate dehydrogenase is responsible, in large part, for observed reperfusion-induced declines in NADH-linked respiration. alpha-Ketoglutarate dehydrogenase is highly susceptible to 4-hydroxy-2-nonenal inactivation in vitro. Thus, our results suggest a plausible mechanism for age-dependent, reperfusion-induced declines in mitochondrial function and identify alpha-ketoglutarate dehydrogenase as a likely site of free radical-mediated damage.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  7. [해외논문]   Regulation of eukaryotic protein synthesis: selective influenza viral mRNA translation is mediated by the cellular RNA-binding protein GRSF-1.  

    Park, Y W , Wilusz, J , Katze, M G
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6694 - 6699 , 1999 , 0027-8424 ,

    초록

    To better understand regulation of eukaryotic protein synthesis, we studied cellular and viral mRNA translation in influenza virus-infected cells. Influenza virus infection results in a dramatic shut-off of cellular protein synthesis that is concomitant with selective viral mRNA translation. Earlier work showed that these events are mediated by viral and/or cellular factors binding to the 5' untranslated region (5' UTR) of viral mRNAs. To identify trans-acting cellular proteins responsible for selective viral protein synthesis, we employed the yeast three-hybrid system. Using the 5' UTR of the influenza virus nucleocapsid protein (NP) mRNA as bait, we identified the cellular RNA-recognition motif containing RNA-binding protein G-rich sequence factor 1 (GRSF-1) as a positive-acting translational regulatory factor. The in vivo yeast assay revealed GRSF-1 specifically bound to the NP 5' UTR but not select NP 5' UTR mutants or cellular RNA 5' UTRs. These data were confirmed by gel shift assays using recombinant GRSF-1. Importantly, recombinant GRSF-1 specifically stimulated translation of a NP 5' UTR-driven template in cell-free translation systems. Furthermore, translation efficiency of NP 5' UTR-driven templates was reduced markedly in GRSF-1-depleted HeLa cell extracts, but restored in GRSF-1-reconstituted extracts. GRSF-1 also stimulated translation of an NP 5' UTR-driven template in HeLa cell extracts that were depleted of essential factors by addition of RNA oligonucleotides representing the viral 5' UTR RNA. Taken together, these data document the functional demonstration of a cellular protein binding to influenza virus RNAs and, importantly, suggest that influenza virus may recruit GRSF-1 to the 5' UTR to ensure preferential translation of viral mRNAs in infected cells.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  8. [해외논문]   Nonlinear optical measurement of membrane potential around single molecules at selected cellular sites.  

    Peleg, G , Lewis, A , Linial, M , Loew, L M
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6700 - 6704 , 1999 , 0027-8424 ,

    초록

    Membrane potential around single molecules has been measured by using the nonlinear optical phenomenon of second harmonic generation. This advance results from the interaction between a highly dipolar molecule with a selectively directed highly polarizable 1-nm gold particle. With this approach, a second harmonic signal, which is enhanced by the nanoparticle, is detected from a volume of nanometric dimensions. This present work clearly shows that functional cellular imaging around single molecules is possible by selectively directing an antibody with a 1-nm gold label to a specific membrane protein. The results of this work open the way for three-dimensional, high resolution functional imaging of membrane electrophysiology in cells and cellular networks.

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  9. [해외논문]   Direct observation of the anchoring process during the adsorption of fibrinogen on a solid surface by force-spectroscopy mode atomic force microscopy  

    Hemmerle, J. , Altmann, S. M. , Maaloum, M. , Horber, J. K. H. , Heinrich, L. , Voegel, J.- C. , Schaaf, P.
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6705 - 6710 , 1999 , 0027-8424 ,

    초록

    Atomic force microscopy in a force-spectroscopy mode has been used to investigate the kinetics of the adsorption process of fibrinogen molecules on a silica surface. An original "approach/retraction" cycle of the tip/surface was used for this purpose. Fibrinogen molecules were adsorbed on the atomic force microscopy tip and were brought into contact with the silica surface for different interaction times varying from 5 to 2,000 ms. Multiple consecutive ruptures were observed. The mean number of ruptures nr per cycle increases steadily with the interaction time as well as the mean strength fr which varies from 300 pN for 5 ms to 1,400 pN for 2,000 ms. The minimal interaction time for a fibrinogen molecule to bind strongly to a silica surface during an adsorption process appears to lie between 50 and 200 ms. The histograms of the distances between two consecutive ruptures in one cycle exhibit maxima around 20-25 nm. This length is comparable to the characteristic distance between D and E globules of one fibrinogen molecule and suggests that fibrinogen molecules mainly adsorb through their D and E globules.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  10. [해외논문]   Osmotic pressure contribution of albumin to colloidal interactions.  

    Singh-Zocchi, M , Andreasen, A , Zocchi, G
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.12 ,pp. 6711 - 6715 , 1999 , 0027-8424 ,

    초록

    Two surfaces that come in close contact in a solution with macromolecules present experience an attractive force caused by the osmotic pressure. We present a measurement of this effect by using a micrometer-sized sphere bound to a flat plate through a single molecular attachment in an albumin-containing solution. We obtain the osmotic part of the interaction potential with a resolution of

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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