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Related Concept Videos

The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
The Proteasome01:13

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Regulation of Nuclear Protein Sorting01:45

Regulation of Nuclear Protein Sorting

Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...

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Related Experiment Video

Updated: Jun 26, 2026

Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
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Substrate requirements for SPPL2b-dependent regulated intramembrane proteolysis.

Lucas Martin1, Regina Fluhrer, Christian Haass

  • 1Center for Integrated Protein Science Munich and Adolf-Butenandt-Institute, Department of Biochemistry, Laboratory for Neurodegenerative Disease Research, Ludwig-Maximilians-University, 80336 Munich, Germany.

The Journal of Biological Chemistry
|December 31, 2008
PubMed
Summary

Intramembrane proteolysis, crucial for cell signaling and protein breakdown, requires specific substrate features. Shedding by ADAM-10 facilitates processing by SPPL2b proteases, but sequence determinants are key.

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Last Updated: Jun 26, 2026

Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
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Published on: September 28, 2018

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08:59

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Determining Membrane Protein Topology Using Fluorescence Protease Protection (FPP)
08:14

Determining Membrane Protein Topology Using Fluorescence Protease Protection (FPP)

Published on: April 20, 2015

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cell Biology

Background:

  • Intramembrane proteolysis is vital for physiological processes like reverse signaling and membrane protein degradation.
  • GXGD-type aspartyl proteases, including signal peptide peptidase-like (SPPL) peptidases, regulate health and disease.
  • Substrate requirements for SPPL2a/b mediated intramembrane proteolysis remain largely unknown.

Purpose of the Study:

  • To investigate the substrate requirements for efficient intramembrane proteolysis by SPPL2b.
  • To determine the role of ectodomain shedding and specific protein domains in SPPL2b substrate processing.

Main Methods:

  • Analysis of Bri2 (Itm2b) and Bri3 (Itm2c) processing, including ectodomain shedding by ADAM-10.
  • Serial deletion and domain swapping experiments to identify critical sequence determinants.
  • Assessment of intramembrane proteolysis by SPPL2b.

Main Results:

  • ADAM-10-mediated shedding facilitates intramembrane proteolysis of Bri2, with ectodomain length being inversely correlated with processing efficiency.
  • Bri3, unlike Bri2, fails to be shed by ADAM-10, resulting in a lack of SPPL2b-mediated intramembrane proteolysis.
  • Specific primary sequence determinants in the intracellular, transmembrane, and juxtamembrane luminal domains are essential for efficient SPPL2b processing, independent of shedding.

Conclusions:

  • Efficient intramembrane proteolysis by SPPL2b depends on both initial shedding and specific sequence elements within the substrate.
  • The failure of Bri3 processing highlights the intricate requirements for SPPL2b substrates.
  • Understanding these determinants is crucial for deciphering the roles of intramembrane proteolysis in cellular functions and disease.