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Related Concept Videos

Electron Transport Chain: Complex I and II01:46

Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
Electron Transport Chain Components01:29

Electron Transport Chain Components

The electron transport chain (ETC) is a crucial metabolic pathway that facilitates energy conversion in prokaryotic and eukaryotic cells. In eukaryotes, the ETC comprises four membrane-associated protein complexes in the inner mitochondrial membrane. In prokaryotes, the ETC in the plasma membrane can vary in composition, with fewer or different complexes depending on the organism and environmental conditions. These complexes transfer electrons from electron donors, such as NADH and FADH2, to...
Protein Complexes with Interchangeable Parts01:57

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
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The Supercomplexes in the Crista Membrane01:41

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The mitochondrial cristae membrane is the primary site for the oxidative phosphorylation (OXPHOS) process of energy conversion mediated through respiratory complexes I to V. These complexes have been widely studied for decades, and it has been proven that they form supramolecular structures called respiratory supercomplexes (SC). These higher-order complexes may be crucial in maintaining the biochemical structure and improving the physiological activity of the individual complexes while...
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The final stage of cellular respiration is oxidative phosphorylation that consists of two steps: the electron transport chain and chemiosmosis. The electron transport chain is a set of proteins found in the inner mitochondrial membrane in eukaryotic cells. Its primary function is to establish a proton gradient that can be used during chemiosmosis to produce ATP and generate electron carriers, such as NAD+ and FAD, that are used in glycolysis and the citric acid cycle.
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Updated: Jul 4, 2026

Tandem Affinity Purification of Protein Complexes from Eukaryotic Cells
11:30

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Published on: January 26, 2017

The multi-tasking P-TEFb complex.

Vanessa Brès1, Sunnie M Yoh, Katherine A Jones

  • 1Regulatory Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037-1099, USA.

Current Opinion in Cell Biology
|June 3, 2008
PubMed
Summary

Positive transcription elongation factor b (P-TEFb) is a key kinase regulating gene expression. It coordinates transcription, RNA processing, export, and translation, integrating multiple cellular processes.

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Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • P-TEFb (CycT1:Cdk9) is a crucial kinase for RNA polymerase II CTD phosphorylation at Ser2.
  • It plays a central role in transcription elongation, linking mRNA synthesis to histone modification, processing, and export.

Purpose of the Study:

  • To elucidate the regulatory mechanisms and functional interactions of P-TEFb in gene expression.
  • To understand how P-TEFb integrates transcription with other cellular processes like histone modification and mRNA export.

Main Methods:

  • The study likely involves biochemical assays, genetic manipulation, and molecular biology techniques to investigate protein interactions and functional roles.
  • Analysis of P-TEFb recruitment, activity, and downstream effects on transcription and mRNA processing.

Main Results:

  • P-TEFb recruitment depends on H2Bub deubiquitination, H3S10 phosphorylation, and Brd4.
  • Brd4 tethers P-TEFb to mitotic chromosomes and activates growth genes.
  • P-TEFb collaborates with c-Myc and requires SKIP for its function.
  • Spt6 and Iws1 complex executes some P-TEFb functions, influencing chromatin and mRNA export.
  • P-TEFb accompanies mRNA to the cytoplasm to promote translation elongation.

Conclusions:

  • P-TEFb is a master regulator integrating transcription, chromatin modification, and mRNA export/translation.
  • Its recruitment and function are tightly controlled by multiple factors, including Brd4, Spt6, and Iws1.
  • P-TEFb's role extends from transcription initiation to translation, highlighting its fundamental importance in gene expression regulation.