Name: how proteins shift shape together
Uploaded: 2023-04-30T18:28:42.000Z
Duration: 1 min 58 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

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

From Molecules to Organisms- Structures and Processes

LS.Bio.1.2

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

Energy and Catalysis

Énergie et catalyse

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how proteins shift shape together

Proteins can change shape in a coordinated way during allosteric transitions. In a cooperative transition, one part of the protein affects another part, so the change spreads through the molecule.

These shape changes help proteins switch between different states. The shift can influence how the protein works and how it responds to other molecules.

Cooperative allosteric transitions are an important idea in protein function. They explain how a small change at one site can lead to a larger change across the protein structure.

How Proteins Shift Shape Together

the first law of thermodynamics

Energy Changes in Cells and Matter

The first law of thermodynamics describes how energy changes form in the universe. The total amount of energy stays constant. Energy can move from one place to another or change into a different form, but it cannot be created or destroyed. These energy changes happen in everyday life. A light bulb changes electrical energy into light energy. A gas stove changes chemical energy in natural gas into heat energy. Plants also carry out a major energy transformation when they convert sunlight energy...

the second law of thermodynamics

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entropy within the cell

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the equilibrium binding constant and binding strength

the-equilibrium-binding-constant-and-binding-strength

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free energy and equilibrium

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non-equilibrium in the cell

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oxidation and reduction of organic molecules

oxidation-and-reduction-of-organic-molecules

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introduction-to-mechanisms-of-enzyme-catalysis

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ligand binding and linkage

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cooperative allosteric transitions

Proteins can change shape in a coordinated way during allosteric transitions. In a cooperative transition, one part of the protein affects another part, so the change spreads through the molecule. These shape changes help proteins switch between different states. The shift can influence how the protein works and how it responds to other molecules. Cooperative allosteric transitions are an important idea in protein function. They explain how a small change at one site can lead to a larger...

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key terms and concepts

Explore cooperative allosteric transitions and how protein shape changes can spread through a molecule to affect protein function in high school biology.

How Proteins Shift Shape Together | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.c

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.4

SC.912.L.18.11

Texas Essential Knowledge and Skills

BIO.11

BIO.11.B

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LS.Bio.1.1

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Ligand Binding and Linkage

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LS.Bio.1.3

Analyze how the relationship between structure and function supports life processes within organisms.

How Proteins Shift Shape Together

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