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Related Concept Videos

Insulin: The Receptor and Signaling Pathways01:28

Insulin: The Receptor and Signaling Pathways

Insulin action is mediated through a receptor tyrosine kinase, akin to the IGF-1 receptor. The number of receptors per cell varies significantly, from 40 on erythrocytes to 300,000 on adipocytes and hepatocytes. The insulin receptor consists of linked α/β subunit dimers, forming a heterotetramer glycoprotein with two extracellular α subunits and two β subunits spanning the membrane. The α subunits inhibit the inherent tyrosine kinase activity of the β subunits, but this inhibition is released...
Protein and Protein Structure02:15

Protein and Protein Structure

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective. They may serve in transport, storage, or membranes; or they may be toxins or enzymes. Their structures, like their functions, vary greatly. They are all, however, amino acid polymers arranged in a linear sequence.
A protein's shape is critical to its function. For example, an enzyme can...
Insulin: Biosynthesis, Chemistry, and Preparation01:25

Insulin: Biosynthesis, Chemistry, and Preparation

The endoplasmic reticulum (ER) of pancreatic β-cells synthesizes preproinsulin, which consists of a signal peptide, A and B chains, and a C-peptide. Preproinsulin is then cleaved and folded into proinsulin, which translocates to the Golgi apparatus for sorting and packaging into secretory granules. In these granules, enzymatic clipping generates insulin and C-peptide.
Damage or functional impairment of β-cells inhibits insulin production, leading to diabetes. Diabetes treatment primarily uses...
Insulin Secretory Vesicles01:05

Insulin Secretory Vesicles

Insulin secretory vesicles release insulin to stimulate blood glucose uptake and regulate carbohydrate metabolism. When the blood glucose levels increase, glucose enters the pancreatic β-islet cells through glucose transporters. Once inside, glucose is metabolized through glycolysis, the citric acid cycle, and the electron transport chain, producing ATP. This increase in ATP concentration closes ATP-sensitive potassium channels, leading to depolarization of the membrane and the opening of...
Glucose Homeostasis: Pancreatic Islets and Insulin Secretion01:27

Glucose Homeostasis: Pancreatic Islets and Insulin Secretion

The pancreatic islets comprising only 1%-2% of the volume are highly vascularized and innervated mini-organs. They contain five endocrine cell types, including β cells that secrete insulin, which is synthesized as a single polypeptide chain, preproinsulin, processed to proinsulin, and finally to insulin and C-peptide. This process is complex and regulated, involving the Golgi complex, the endoplasmic reticulum, and the secretory granules of the β cell.
Insulin and C-peptide are co-secreted in...
Protein Translocation Machinery on the ER Membrane01:28

Protein Translocation Machinery on the ER Membrane

The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.

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Related Experiment Video

Updated: Jun 25, 2026

Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion
07:30

Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion

Published on: May 10, 2018

The structure and function of insulin: decoding the TR transition.

Michael A Weiss1

  • 1Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA.

Vitamins and Hormones
|March 3, 2009
PubMed
Summary
This summary is machine-generated.

Insulin

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Precise Visualization of Insulin Receptors A and B in Murine Brain with an RNA In Situ Hybridization Assay
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Precise Visualization of Insulin Receptors A and B in Murine Brain with an RNA In Situ Hybridization Assay

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Confocal Imaging of Neuropeptide Y-pHluorin: A Technique to Visualize Insulin Granule Exocytosis in Intact Murine and Human Islets
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Confocal Imaging of Neuropeptide Y-pHluorin: A Technique to Visualize Insulin Granule Exocytosis in Intact Murine and Human Islets

Published on: September 13, 2017

Related Experiment Videos

Last Updated: Jun 25, 2026

Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion
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Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion

Published on: May 10, 2018

Precise Visualization of Insulin Receptors A and B in Murine Brain with an RNA In Situ Hybridization Assay
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Precise Visualization of Insulin Receptors A and B in Murine Brain with an RNA In Situ Hybridization Assay

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Confocal Imaging of Neuropeptide Y-pHluorin: A Technique to Visualize Insulin Granule Exocytosis in Intact Murine and Human Islets
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Confocal Imaging of Neuropeptide Y-pHluorin: A Technique to Visualize Insulin Granule Exocytosis in Intact Murine and Human Islets

Published on: September 13, 2017

Area of Science:

  • Protein crystallography
  • Molecular biology
  • Endocrinology

Background:

  • Insulin exhibits distinct hexameric structures (T(6), T(3)R(3)(f), R(6)) with a T-R transition.
  • The biological significance of this structural transition and allostery is not fully understood.

Purpose of the Study:

  • To investigate the biological implications of insulin's structural transitions.
  • To explore the relationship between insulin's conformational states, stability, and receptor binding.
  • To understand the role of conformational changes in proinsulin folding and diabetes.

Main Methods:

  • Analysis of existing insulin crystal structures.
  • Stereospecific d- and l-amino acid substitutions.
  • Assessment of protein stability and receptor-binding activity.

Main Results:

  • Insulin's T-R transition involves a switch between folding-competent and active conformations.
  • Amino acid substitutions stereospecifically modulate stability and receptor binding.
  • Human mutations at conformational sites cause proinsulin folding defects and neonatal diabetes.

Conclusions:

  • Insulin's crystal structures reveal its in vivo conformational lifecycle.
  • Protein crystallography provides insights into biological functions beyond crystallization conditions.
  • Understanding insulin's receptor-bound structure could lead to new diabetes treatments.