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Proceedings of the National Academy of Sciences of... 104건

  1. [해외논문]   BglG, the transcriptional antiterminator of the bgl system, interacts with the ' subunit of the Escherichia coli RNA polymerase  

    Nussbaum-Shochat, A. , Amster-Choder, O.
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4336 - 4341 , 1999 , 0027-8424 ,

    초록

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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.

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  2. [해외논문]   Universal conservation in translation initiation revealed by human and archaeal homologs of bacterial translation initiation factor IF2.  

    Lee, J H , Choi, S K , Roll-Mecak, A , Burley, S K , Dever, T E
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4342 - 4347 , 1999 , 0027-8424 ,

    초록

    Binding of initiator methionyl-tRNA to ribosomes is catalyzed in prokaryotes by initiation factor (IF) IF2 and in eukaryotes by eIF2. The discovery of both IF2 and eIF2 homologs in yeast and archaea suggested that these microbes possess an evolutionarily intermediate protein synthesis apparatus. We describe the identification of a human IF2 homolog, and we demonstrate by using in vivo and in vitro assays that human IF2 functions as a translation factor. In addition, we show that archaea IF2 can substitute for its yeast homolog both in vivo and in vitro. We propose a universally conserved function for IF2 in facilitating the proper binding of initiator methionyl-tRNA to the ribosomal P site.

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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.

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  3. [해외논문]   The membrane-attached electron carrier cytochrome cy from Rhodobacter sphaeroides is functional in respiratory but not in photosynthetic electron transfer.  

    Myllykallio, H , Zannoni, D , Daldal, F
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4348 - 4353 , 1999 , 0027-8424 ,

    초록

    Rhodobacter species are useful model organisms for studying the structure and function of c type cytochromes (Cyt c), which are ubiquitous electron carriers with essential functions in cellular energy and signal transduction. Among these species, Rhodobacter capsulatus has a periplasmic Cyt c2Rc and a membrane-bound bipartite Cyt cyRc. These electron carriers participate in both respiratory and photosynthetic electron-transfer chains. On the other hand, until recently, Rhodobacter sphaeroides was thought to have only one of these two cytochromes, the soluble Cyt c2Rs. Recent work indicated that this species has a gene, cycYRs, that is highly homologous to cycYRc, and in the work presented here, functional properties of its gene product (Cyt cyRs) are defined. It was found that Cyt cyRs is unable to participate in photosynthetic electron transfer, although it is active in respiratory electron transfer, unlike its R. capsulatus counterpart, Cyt cyRc. Chimeric constructs have shown that the photosynthetic incapability of Cyt cyRs is caused, at least in part, by its redox active subdomain, which carries the covalently bound heme. It, therefore, seems that this domain interacts differently with distinct redox partners, like the photochemical reaction center and the Cyt c oxidase, and allows the bacteria to funnel electrons efficiently to various destinations under different growth conditions. These findings raise an intriguing evolutionary issue in regard to cellular apoptosis: why do the mitochondria of higher organisms, unlike their bacterial ancestors, use only one soluble electron carrier in their respiratory electron-transport chains?

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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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  4. [해외논문]   The NDUFA1 gene product (MWFE protein) is essential for activity of complex I in mammalian mitochondria.  

    Au, H C , Seo, B B , Matsuno-Yagi, A , Yagi, T , Scheffler, I E
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4354 - 4359 , 1999 , 0027-8424 ,

    초록

    The MWFE polypeptide of mammalian complex I (the proton-translocating NADH-quinone oxidoreductase) is 70 amino acids long, and it is predicted to be a membrane protein. The NDUFA1 gene encoding the MWFE polypeptide is located on the X chromosome. This polypeptide is 1 of approximately 28 "accessory proteins" identified in complex I, which is composed of 42 unlike subunits. It was considered accessory, because it is not one of the 14 polypeptides making up the core complex I; a homologous set of 14 polypeptides can make a fully functional proton-translocating NADH-quinone oxidoreductase in prokaryotes. One MWFE mutant has been identified and isolated from a collection of respiration-deficient Chinese hamster cell mutants. The CCL16-B2 mutant has suffered a deletion that would produce a truncated and abnormal MWFE protein. In these mutant cells, complex I activity is reduced severely (

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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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  5. [해외논문]   Acyl homoserine-lactone quorum-sensing signal generation.  

    Parsek, M R , Val, D L , Hanzelka, B L , Cronan, J E , Greenberg, E P
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4360 - 4365 , 1999 , 0027-8424 ,

    초록

    Acyl homoserine lactones (acyl-HSLs) are important intercellular signaling molecules used by many bacteria to monitor their population density in quorum-sensing control of gene expression. These signals are synthesized by members of the LuxI family of proteins. To understand the mechanism of acyl-HSL synthesis we have purified the Pseudomonas aeruginosa RhlI protein and analyzed the kinetics of acyl-HSL synthesis by this enzyme. Purified RhlI catalyzes the synthesis of acyl-HSLs from acyl-acyl carrier proteins and S-adenosylmethionine. An analysis of the patterns of product inhibition indicated that RhlI catalyzes signal synthesis by a sequential, ordered reaction mechanism in which S-adenosylmethionine binds to RhlI as the initial step in the enzymatic mechanism. Because pathogenic bacteria such as P. aeruginosa use acyl-HSL signals to regulate virulence genes, an understanding of the mechanism of signal synthesis and identification of inhibitors of signal synthesis has implications for development of quorum sensing-targeted antivirulence molecules.

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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]   A molecular trigger of lipid binding-induced opening of a helix bundle exchangeable apolipoprotein.  

    Narayanaswami, V , Wang, J , Schieve, D , Kay, C M , Ryan, R O
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4366 - 4371 , 1999 , 0027-8424 ,

    초록

    Apolipophorin III (apoLp-III) from the sphinx moth, Manduca sexta, is a helix bundle protein that interacts reversibly with lipoproteins. Its five elongated amphipathic alpha-helices are organized in an antiparallel fashion, with helices 3 and 4 connected by a short 6-residue (PDVEKE) linker helix, termed helix 3'. Upon interaction with lipoproteins, apoLp-III opens to expose a continuous hydrophobic interior. It was postulated that helix bundle opening is preceded by an initiation step wherein helix 3' serves to recognize available lipoprotein surface binding sites. To test this hypothesis, helix 3' was replaced by residues that have a propensity to form a type I beta-turn, NPNG. This mutant apoLp-III was defective in lipoprotein binding assays. To define a more precise mode of interaction, the relevance of the presence of the hydrophobic Val-97 flanked by Asp-96 and Glu-98 was investigated by site-directed mutagenesis. V97N and D96N/V97N/E98Q apoLp-III were unable to compete with wild-type apoLp-III to initiate an interaction with lipoproteins, whereas D96N/E98Q apoLp-III was as competent as wild-type apoLp-III. The results suggest that Val-97 is critical, whereas Asp-96 and Glu-98 are irrelevant for initiating binding to lipoproteins. A model of binding is presented wherein apoLp-III is oriented with the helix 3' end of the molecule juxtaposed to the lipoprotein surface. Recognition of lipoprotein surface hydrophobic defects by Val-97 triggers opening of the helix bundle and facilitates formation of a stable binding interaction.

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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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  7. [해외논문]   Oligoribonuclease is an essential component of the mRNA decay pathway.  

    Ghosh, S , Deutscher, M P
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4372 - 4377 , 1999 , 0027-8424 ,

    초록

    mRNA decay in prokaryotic cells involves the action of both endo- and exoribonucleases. In Escherichia coli, degradation of RNA to the mononucleotide level was thought to depend on RNase II and polynucleotide phosphorylase. Here, we show that the enzyme oligoribonuclease is an essential part of this process as well. Thus, inactivation of the orn gene encoding oligoribonuclease leads to a cessation of cell growth. Moreover, although pulse-labeled RNA decays normally in orn mutant cells under nonpermissive conditions, a large fraction of the resulting products is small oligoribonucleotides rather than the mononucleotides generated in wild-type cells. The oligoribonucleotides that accumulate are 2-5 residues in length; longer molecules disappear during the decay process. These data indicate that oligoribonuclease is required to complete the degradation of mRNA to mononucleotides and that this process is required for cell viability. Inasmuch as close homologues of the orn gene are found in a wide range of eukaryotes, extending up to humans, these findings raise the possibility that oligoribonuclease also participates in mRNA degradation in these organisms.

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

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  8. [해외논문]   Effects of mutant p53 expression on human 15-lipoxygenase-promoter activity and murine 12/15-lipoxygenase gene expression: evidence that 15-lipoxygenase is a mutator gene.  

    Kelavkar, U P , Badr, K F
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4378 - 4383 , 1999 , 0027-8424 ,

    초록

    Human 15-lipoxygenase (h15-LO) is present on chromosome 17p13.3 in close proximity to the tumor-suppressor gene, p53. 15-LO is implicated in antiinflammation, membrane remodeling, and cancer development/metastasis. The murine BALB/c embryo fibroblast cell line, (10)1val, expresses p53 in mutant (mt) conformation when grown at 39 degrees C and in wild-type conformation when grown at 32 degrees C. Transfection of h15-LO promoter constructs (driving luciferase reporter) into (10)1val cells and into p53-deficient (10)1 cells resulted in a marked increase in h15-LO promoter activity in (10)1val cells at 39 degrees C, but not at 32 degrees C, or as compared with (10)1 cells. Transfection of h15-LO promoter deletion constructs, however, resulted in total loss of activity in both cell types at 32 degrees C and 39 degrees C. Cotransfection of (10)1 cells with h15-LO promoter (driving luciferase reporter) along with increasing levels of a mt p53 expression vector demonstrated dose-dependent capacity of mt p53 to induce 15-LO promoter activity. No effect was observed with wild-type p53. In contrast to h15-LO promoter activity, (10)1val cells had significantly lower levels of endogenous (murine) 12/15-LO (mouse analog of h15-LO) mRNA and protein when grown at 39 degrees C compared with cells grown at 32 degrees C. Our data support the hypothesis that loss of a tumor-suppressor gene (p53), or "gain-of-function activities" resulting from the expression of its mutant forms, regulates 15-LO promoter activity in man and in mouse, albeit in directionally opposite manners. The studies define a direct link between 15-LO activity and an established tumor-suppressor gene located in close chromosomal proximity.

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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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  9. [해외논문]   Triple-helix formation of DNA oligomers with methylthiourea-linked nucleosides (DNmt): a kinetic and thermodynamic analysis.  

    Arya, D P , Bruice, T C
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4384 - 4389 , 1999 , 0027-8424 ,

    초록

    Complementary short-strand DNA homooligomers and methylthiourea-linked homonucleosides associate and form triplexes in solution. The melting temperatures, Tm, the association and dissociation kinetic and thermodynamic parameters, and activation energies were determined by UV thermal analysis for the triplexes of short-strand DNA homooligomers [d(pA)10-d(pA)23] and poly(dA) with the methylthiourea-linked nucleoside [5'-NH3+-d(Tmt)4-T-OH [DNmt5]]. Circular dichroism studies show evidence of triple-helical association dependent on the length of the target homooligomer. The melting and cooling curves exhibit hysteresis behavior in the temperature range of 10-95 degrees C at 0.13 deg/min thermal rate. From these curves, the rate constants and the energies of activation for association (kon, Eon) and dissociation (koff, Eoff) were obtained. Tm decreases with the ionic strength and increases with increase in length of the monomers. The rate constants kon and koff at a given temperature (288 K-310 K) are dependent on the DNA strand length and also decrease and increase respectively with the ionic strength. The energies of activation for the association and dissociation processes are in the range of -18 to -38 kcal/mol and 3 to 18 kcal/mol, respectively. The equilibrium constant for the formation of the triplexes [5'-NH3+-d(Tmt)4-T-OH)2.d(pA)x, x = 10-23] is several orders of magnitude greater when compared with the triplexes of DNA. The number of base triplets in the nucleus of the DNmt2.DNA triple-helix (nucleation-zipping model) increases with decreased DNA oligomer length and with increased ionic strength. The values of DeltaH degrees calculated from the activation parameters are between -30 and -50 kcal/(mol base) and the values of DeltaG degrees are between -6 and -11 kcal/(mol base) for short-strand DNA.

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

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  10. [해외논문]   RNA polymerase switch in transcription of yeast rDNA: role of transcription factor UAF (upstream activation factor) in silencing rDNA transcription by RNA polymerase II.  

    Vu, L , Siddiqi, I , Lee, B S , Josaitis, C A , Nomura, M
    Proceedings of the National Academy of Sciences of the United States of America v.96 no.8 ,pp. 4390 - 4395 , 1999 , 0027-8424 ,

    초록

    Transcription factor UAF (upstream activation factor) is required for a high level of transcription, but not for basal transcription, of rDNA by RNA polymerase I (Pol I) in the yeast Saccharomyces cerevisiae. RRN9 encodes one of the UAF subunits. We have found that rrn9 deletion mutants grow extremely slowly but give rise to faster growing variants that can grow without intact Pol I, synthesizing rRNA by using RNA polymerase II (Pol II). This change is reversible and does not involve a simple mutation. The two alternative states, one suitable for rDNA transcription by Pol I and the other favoring rDNA transcription by Pol II, are heritable not only in mitosis, but also in meiosis. Thus, S. cerevisiae has an inherent ability to transcribe rDNA by Pol II, but this transcription activity is silenced in normal cells, and UAF plays a key role in this silencing by stabilizing the first state.

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

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