Dna helicases

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  • DNA helicases are molecularmotor enzymes that use the energy of NTP hydrolysis to separate transiently energetic-ally stable duplex DNA into single strands. They are there-fore essential in nearly all DNA metabolic transactions. They act as essential molecular tools for the cellular machinery. Since the discovery of the first DNA helicase in Escherichia coliin1976, several havebeen isolated fromboth prokaryotic and eukaryotic systems.

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  • A novel ATP-dependent nuclear DNA unwinding enzyme from pea has been purified to apparent homogeneity and characterized. This enzyme is present at extremely low abundance and has the highest specific activity among plant helicases. It is a heterodimer of 54 and 66 kDa polypeptides as determined by SDS/PAGE. On gel filtration chroma-tography and glycerol gradient centrifugation it gives a native molecular mass of 120 kDa and is named as pea DNA helicase 120 (PDH120).

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  • NA helicases are ubiquitous molecular motor proteins which harness the chemical free energy of ATPhydrolysis to catalyze the unwinding of energetically stable duplex DNA, and thus play important roles in nearly all aspects of nucleic acid metabolism, including replication, repair, recombina-tion, and transcription. They break the hydrogen bonds between the duplex helix and move unidirectionally along the bound strand. All helicases are also translocases and DNA-dependentATPases.Most contain conserved helicase motifs that act as an engine to power DNA unwinding. ...

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  • The faithful and complete replication of chromosomes is essential to maintain genetic stability and prevent the accumulation of cancer-promoting mutations. Replication forks are vulnerable to stalling or collapse as they encounter obstacles on the DNA template, which can be unrepaired DNA damage, DNA-bound proteins or secondary structures. Similarly, chemical agents like hydroxyurea and aphidicolin inhibit replication elongation, leading to fork stalling or collapse.

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  • Replicative helicases are major motor proteins essential for chromosomal DNA replication in prokaryotes. Usually hexameric in solution, their DNA binding property must have different roles at stages ranging from the load-ing onto a branched structure at initiation from the origin to the highly pro-cessive translocation during elongation.

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  • The antibiotic heliquinomycin, which inhibits cellular DNA replication at a half-maximal inhibitory concentration (IC50) of 1.4–4lm, was found to inhi-bit the DNA helicase activity of the human minichromosome maintenance (MCM) 4/6/7 complex at an IC50value of 2.4lm. In contrast, 14 lmheliqui-nomycin did not inhibit significantly either the DNA helicase activity of the SV40 T antigen and Werner protein or the oligonucleotide displacement activity of human replication protein A.

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  • The humanSUV3gene encodes an NTP-dependent DNA⁄RNA DExH box helicase predominantly localized in mitochondria. Its orthologue in yeast is a component of the mitochondrial degradosome complex involved in the mtRNA decay pathway. In contrast to this, the physiological func-tion of human SUV3remains to be elucidated. In this report we demon-strate that the hSuv3 protein interacts with HBXIP, previously identified as a cofactor of survivin in suppression of apoptosis and as a protein that binds the HBx protein encoded by the hepatitis B virus....

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  • DNA gyrase, thường được gọi đơn giản là gyrase, là một enzyme làm giảm căng thẳng khi hai sợi DNA đang được unwound bởi helicase. Điều này gây ra supercoiling của DNA. Nhiều loại thuốc kháng sinh làm việc bằng cách tấn công DNA gyrase của vi khuẩn. DNA gyrase là một loại topoisomerase II ( EC 5.99.1.

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  • Tái bản DNA (DNA Replication) hay quá trình nhân đôi hệ gene của cơ thể, là điều bắt buộc khi tế bào phân chia. Tái bản, cũng giống như mọi hoạt động tế bào, đòi hỏi những protein chuyên biệt để tiến hành công việc. Trong bước đầu tiên của tái bản, một protein chuyên biệt, gọi là helicase, tháo một phần mạch DNA xoắn kép bố mẹ.

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  • Hexameric DnaB helicase unwinds the DNA double helix during replica-tion of genetic material in bacteria. DnaB is an essential bacterial protein; therefore, it is an important potential target for antibacterial drug disco-very. We report a crystal structure of the N-terminal region of DnaB from the pathogen Mycobacterium tuberculosis(MtDnaBn), determined at 2.0 A˚ resolution.

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  • DnaG is the primase that lays down RNA primers on single-stranded DNA during bacterial DNA replication. The solution structure of the DnaB-helicase-binding C-terminal domain ofEscherichia coliDnaG was determined by NMR spectroscopy at near-neutral pH. The structure is a rare fold that, besides occurring in DnaG C-terminal domains, has been described only for the N-terminal domain of DnaB.

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  • RNA helicase A (RHA), a member of DNA and RNA helicase family containing ATPase activity, is involved in many steps of gene expression such as transcription and mRNA export. RHA has been reported to bind directly to the transcriptional coactivator, CREB-binding protein, and the tumor suppressor protein, BRCA1, and links them to RNAPolymerase II holoenzyme complex. Using yeast two-hybrid screening, we have identified RHA as an interacting molecule of the p65 subunit of nuclear factorjB(NF-jB).

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  • The chapter describe the contributions of the following people: Griffith; Avery, McCary, and MacLeod; Hershey and Chase; Chargaff; Watson and Crick; Franklin; Meselson and Stahl; describe the structure of DNA; describe the process of DNA replication; include the following terms: antiparallel structure, DNA polymerase, leading strand, lagging strand, Okazaki fragments, DNA ligase, primer, primase, helicase, topoisomerase, single-strand binding proteins.

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  • Helicobacter pylori, an important bacterial pathogen, causes gastric ulcer and gastric adenocarcinoma in humans. The fundamentals of basic biology such as DNA replication are poorly understood in this pathogen. In the present study, we report the cloning and functional characterization of the single-stranded DNA (ssDNA) binding protein from H. pylori.

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  • A search has been initiated for lead inhibitors of the non-structural protein 3 (NS3)-associated NTPase/helicase activities of hepatitis C virus,the related West Nile virus, Japanese encephalitis virus and the human mitochondrial Suv3 enzyme. Random screening of a broad range of unre-lated low-molecular mass compounds,employing both RNA and DNA substrates, revealed that 4,5,6,7-tetra-bromobenzotriazole (TBBT) hitherto known as a potent highly selective inhibitor of protein kinase 2,is a good inhibitor of the helicase,but not NTPase,activity of hepa-titis C virus NTPase/helicase. ...

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  • Chapter 16 - The molecular basis of inheritance. The chapter describe the contributions of the following people: Griffith; Avery, McCary, and MacLeod; Hershey and Chase; Chargaff; Watson and Crick; Franklin; Meselson and Stahl; describe the structure of DNA; describe the process of DNA replication; include the following terms: antiparallel structure, DNA polymerase, leading strand, lagging strand, Okazaki fragments, DNA ligase, primer, primase, helicase, topoisomerase, single-strand binding proteins.

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  • + Topoizomerase làm nhiệm vụ mở xoắn của ADN làm cho phân tử ADN duỗi thẳng ra. + Helicase làm nhiệm vụ phân huỷ các liên kết hydro để tách 2 chuỗi polynucleotide rời nhau ra. + AND - ligase làm nhiệm vụ nối các đoạn AND - okasaki lại. + ARN - polymerase (primase) xúc tác tổng hợp đoạn ARN mồi. - Các loại protein: tham gia tái sinh ADN có nhiều loại protein đặc hiệu như protein SSB, protein Dna .... 12.2.2. Cơ chế tái sinh ADN Quá trình tái sinh ADN ở procariote xảy ra qua ba...

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  • MCM4, a subunit of a putative replicative helicase, is phosphorylated dur-ing the cell cycle, at least in part by cyclin-dependent kinases (CDK), which play a central role in the regulation of DNA replication. However, detailed characterization of the phosphorylation of MCM4 remains to be per-formed.

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  • Functional cooperation between FACT and the MCM helicase complex constitutes an integral step during DNA replication initiation. However, mode of regulation that underlies the proper functional interaction of FACT and MCM is poorly understood. Methods & Results: Here we present evidence indicating that such interaction is coordinated with cell cycle progression and differential complex formation. We first demonstrate the existence of two distinct FACT-MCM subassemblies, FACT-MCM2/4/6/7 and FACT-MCM2/3/4/5. Both complexes possess DNA unwinding...

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  • The human 57 kDa Ki-1 antigen (Ki-1⁄57) is a cytoplasmic and nuclear protein, associated with Ser⁄Thr protein kinase activity, and phosphorylat-ed at the serine and threonine residues upon cellular activation. We have shown that Ki-1⁄57 interacts with chromo-helicase DNA-binding domain protein 3 and with the adaptor⁄signaling protein receptor of activated kinase 1 in the nucleus.

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