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Related Concept Videos

Mutual Inductance01:24

Mutual Inductance

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Inductance is the property of a device that tells us how effectively it induces an emf in another device. In other words, it is a physical quantity that expresses the effectiveness of a given device.
When two circuits carrying time-varying currents are close to one another, the magnetic flux through each circuit varies because of the changing current in the other circuit. Consequently, an emf is induced in each circuit by the changing current in the other. Therefore, this type of emf is called...
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E2 Reaction: Stereochemistry and Regiochemistry02:43

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Elimination reactions of alkyl halides can yield one or more alkenes depending on the specific regiochemical and stereochemical considerations. While the regiochemistry of the reaction governs the location of the double bond in the product, the stereochemical requirements often influence the geometry.
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major...
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E2 Reaction: Kinetics and Mechanism02:45

E2 Reaction: Kinetics and Mechanism

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SN2 substitutions and E2 eliminations of alkyl halides proceed via a concerted pathway. While the nucleophile attacks the alpha carbon in SN2 reactions, it functions as a strong base and abstracts a beta hydrogen in the E2 mechanism. The rate-limiting transition state in E2 elimination reactions is characterized by partially broken carbon–hydrogen and carbon–halogen bonds and a partially formed pi bond between the alpha and beta carbons. The beta hydrogen and halide are eliminated...
12.5K
E1 Reaction: Kinetics and Mechanism02:46

E1 Reaction: Kinetics and Mechanism

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Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only...
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E1 Reaction: Stereochemistry and Regiochemistry02:43

E1 Reaction: Stereochemistry and Regiochemistry

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One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
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Subcellular Fractionation01:32

Subcellular Fractionation

8.9K
The homogenate obtained after cell lysis contains various membrane-bound organelles that can be further separated into pure fractions by subcellular fractionation. These isolates are used to study specific cellular components, analyze localized protein activity, and are even employed in diagnostics. Fractionation is typically achieved using centrifugation methods, the most common being density-gradient and differential centrifugation.
Differential Centrifugation
Differential centrifugation is...
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Visualizing Subcellular Localization of a Protein in the Heart Using Quantum Dots-Mediated Immuno-Labeling Followed by Transmission Electron Microscopy
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Cottontail Rabbit Papillomavirus E1 and E2 Proteins Mutually Influence Their Subcellular Localizations.

Markus Schneider1, Aylin Yigitliler1, Frank Stubenrauch1

  • 1University Hospital Tuebingen, Institute for Medical Virology and Epidemiology of Viral Diseases, Tuebingen, Germany.

Journal of Virology
|August 24, 2018
PubMed
Summary

Papillomavirus E1 and E2 proteins regulate viral DNA replication and transcription. Mutated E2 proteins, when coexpressed with E1, can localize to the nucleus and restore viral reporter gene activity, revealing novel E1-E2 interactions.

Keywords:
E1E2nuclear localizationpapillomavirusreplication

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Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4',6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans
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Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4',6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans

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Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • Papillomavirus (PV) E1 and E2 proteins are essential for viral genome replication and transcription.
  • E2 is a nuclear DNA-binding protein regulating viral transcription and genome retention.
  • Both E1 and E2 proteins possess nuclear localization signals (NLS) for nuclear import.

Purpose of the Study:

  • To investigate the role of conserved E2 residue K111 in PV nuclear transport, transcription, and replication.
  • To elucidate the interplay between E1 and E2 proteins in controlling their subcellular localization.
  • To understand the functional consequences of E2 K111 mutations on PV replication and transcription.

Main Methods:

  • Site-directed mutagenesis of the Cottontail rabbit PV (CRPV) E2 K111 residue (to R, A, or Q).
  • Expression of wild-type and mutant E1 and E2 proteins in cell culture.
  • Confocal microscopy to determine protein localization.
  • Reporter gene assays to assess transcriptional activation.

Main Results:

  • CRPV E2 K111 mutants were transcription-deficient and localized to the cytoplasm.
  • Addition of an NLS restored nuclear localization of E2 K111 mutants but not transcriptional activity, suggesting impaired Brd4 binding.
  • Coexpression with E1 rescued nuclear localization of E2 K111 mutants and restored reporter gene activity for K111A and K111R.
  • E1 could direct cytoplasmic E2 mutants to the nucleus independently of E2's NLS or direct binding.
  • Wild-type E2 could direct cytoplasmic E1 NLS mutants to the nucleus, dependent on E1-E2 interaction.

Conclusions:

  • E1 and E2 proteins exhibit mutual control over their subcellular localization.
  • E2 binding to E1 can mediate E1 nuclear import independently of the E1 NLS.
  • E1 can mediate E2 nuclear import independently of E2's NLS or direct binding, indicating a novel E1 function.
  • These findings reveal a complex regulatory mechanism for PV replication and transcription.