Name: allosteric changes in protein shape
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 1 min 58 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Cooperative Allosteric Transitions

Beaucoup de protéines ont plusieurs sous-unités où chacune contient un site de liaison au ligand distinct. Lorsqu'une molécule est appelée modulateur se lie à l'une des sous-unités, elle déclenche un changement conformationnel dans les sites de liaison des autres sous-unités, modifiant leur affinité pour leurs ligands respectifs. C'est ce qu'on appelle une transition allostérique coopérative et peut être expliquée par plusieurs modèles théoriques.Le modèle concerté ou du tout ou rien suppose que toutes les sous-unités existent ensemble dans une conformation off ou on. Une liaison peut se produire sous n'importe quelle forme. Cependant, l'état on a une affinité plus élevée pour le ligand que l'état off.Lorsqu'un ligand se lie à l'une des sous-unités, il favorise la transformation simultanée de tous les sites liaison à la forme de haute affinité. La coopération peut aussi être expliquée par le modèle séquentiel, qui suppose que chaque sous-unité peut exister indépendamment dans un état d'affinité élevé ou faible mais est plus susceptible d'être dans l'état de haute affinité lorsque le ligand est lié à l'une des sous-unités. Les sites de liaison des protéines allostériques sont généralement un mélange de segments flexibles et fixes de la chaîne des acides aminés.Lorsqu'un ligand se lie, ces parties instables sont stabilisés dans une conformation particulière. Et cela affecte la forme des sites de liaison sur les autres sous-unités. L'hémoglobine est un exemple d'une protéine tétramère qui subit une transition allostérique coopérative quand l'oxygène s'y lie.Chaque sous-unité d'hémoglobine possède un seul site de liaison. Lorsqu'une molécule d'oxygène se lie à une seule sous-unité, la coopération augmente l'affinité pour l'oxygène sur les sites liaison restants, facilitant ainsi, la liaison de l'oxygène à une molécule d'hémoglobine qui a déjà de l'oxygène lié à elle.

<ol>
	<li>Cornish‐Bowden, A. (2014), Comprendre les interactions allostériques et coopératives dans les enzymes. FEBS J, 281 : 621-632. doi :10.1111/febs.12469</li>
	<li>Alberts et al., 6e édition ; pages 152-153</li>
	<li>Principes de biochimie de Lehninger, 5e édition, pages 162,165</li>
</ol>

coopérativité

Des transitions allostériques coopératives peuvent se produire dans les protéines multimères, où chaque sous-unité de la protéine possède son propre site de liaison au ligand. Lorsqu'un ligand se lie à l'une de ces sous-unités, il déclenche un changement conformationnel qui affecte les sites de liaison des autres sous-unités ; cela peut modifier l'affinité des autres sites pour leurs ligands respectifs. La capacité de la protéine à modifier la forme de son site de liaison est attribuée à la présence d’un mélange de segments flexibles et stables dans la structure. Une molécule qui déclenche ce changement est appelée modulateur.

Deux modèles sont souvent utilisés pour expliquer la coopérativité dans les protéines multimériques : le modèle concerté et le modèle séquentiel. Le modèle concerté, également connu sous le nom de modèle tout ou rien, émet l’hypothèse que toutes les sous-unités d’une protéine multimérique commutent simultanément entre les conformations « on » et « off ». Sous la forme « on », les sites de liaison ont une forte affinité pour leurs ligands respectifs, et sous la forme « off », les sites de liaison ont une faible affinité. Lorsqu'un ligand se lie à l'une des sous-unités, il favorise la conversion vers la forme de haute affinité, modifiant simultanément la conformation de tous les autres sites de liaison de la protéine. Bien qu'un ligand puisse se lier à l'une ou l'autre forme, il lui est plus facile de se lier sous la forme à haute affinité.

Le modèle séquentiel suppose que chaque sous-unité d’une protéine multimérique peut exister indépendamment dans une conformation « on » ou « off », c’est-à-dire sous la forme de faible ou de haute affinité, quel que soit l’état des autres sous-unités. La liaison d'un ligand à une sous-unité modifie l'équilibre entre les formes de faible et de haute affinité, de sorte qu'il est plus probable que la sous-unité soit sous une forme de haute affinité. De plus, la liaison d'un ligand sur une sous-unité modifie l'équilibre des autres sous-unités de la protéine. Cela augmente la probabilité qu'une fois qu'un ligand est lié, un autre ligand se lie à une sous-unité différente. Cette coopérativité augmente la sensibilité de la protéine à la concentration du ligand. La liaison d'un ligand sur un site unique peut modifier l'affinité sur la molécule protéique entière, permettant ainsi une réponse rapide à de faibles concentrations.

Coopérativité

Des transitions allostériques coopératives peuvent se produire dans les protéines multimériques, où chaque sous-unité de la protéine a son propre site de liaison au ligand. Lorsqu’un ligand ...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Protein Function

Fonction des protéines

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

allosteric changes in protein shape

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule.

The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens step by step across the protein.

These models help students understand how proteins respond to signals in the cell. They also show why protein shape is closely linked to biological activity.

Allosteric Changes in Protein Shape

ligand binding sites

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protein-protein interfaces

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conserved binding sites

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cooperative allosteric transitions

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule. The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens...

protein kinases and phosphatases

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gtpases and their regulation

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covalently linked protein regulators

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protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

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mechanical protein function

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structural protein function

Structural Proteins in Cells and Tissues

Structural proteins help cells and tissues keep their shape and strength. They are an important part of living systems because they provide support where it is needed most. Many structural proteins form fibers or other sturdy forms that resist stretching and wear. These proteins work as building materials in the body and help keep structures stable over time. Examples of structural proteins include collagen, actin, myosin, and keratin. Each one supports a different part of the body, but all...

protein networks

Mapping Protein Interaction Networks

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key terms and concepts

Explore cooperative allosteric transitions and learn how protein shape changes can switch proteins between active and inactive states using concerted and sequential models.

Allosteric Changes in Protein Shape | JoVE K12

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HS-LS1-3

Allosteric Changes in Protein Shape

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