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

Molte proteine hanno subunità multiple dove ogni subunità contiene un sito di legame del ligando separato. Quando una molecola nota come modulatore si lega ad una delle subunità, attiva un cambiamento conformazionale nei siti di legame delle altre subunità, cambiando la loro affinità per i rispettivi ligandi. Questo processo é definito una transizione allosterica cooperativa e può essere spiegato tramite diversi modelli teorici.Il modello convenuto tutti-o-nessuno presuppone che tutte le subunità abbiano insieme un off o un on confermati. Il legame può avvenire in entrambe le forme, tuttavia, lo stato on ha un'affinità più elevata per il ligando rispetto allo stato off. Quando un ligando si lega ad una qualsiasi delle subunità, promuove la trasformazione simultanea di tutti i siti di legame alla forma ad alta affinità;può essere spiegato in modo cooperativo anche dal modello sequenziale, che presuppone che ogni subunità possa esistere indipendentemente in uno stato di alta o bassa affinità, ma è più probabile che sia nello stato di alta affinità quando il ligando è legato a una qualsiasi delle subunità.I siti di legame delle proteine allosteriche sono solitamente una miscela di segmenti flessibili e fissi della catena amminoacidica;quando un ligando si lega, queste parti instabili sono stabilizzate in una particolare conformazione, influenzando la forma dei siti di legame sulle altre subunità. L'emoglobina è un esempio di una proteina tetramerica che subisce una transizione allosterica cooperativa quando si lega all'ossigeno. ogni subunità di emoglobina ha un singolo sito di legame.quando una molecola di ossigeno si lega ad una singola subunità, aumenta cooperativamente l'affinità per l'ossigeno sui siti di legame rimanenti, rendendo più facile per l'ossigeno legarsi 00:01:52.110 00:01:57.500 ad una molecola di emoglobina che ha già ossigeno legato ad essa.

<ol>
	<li>Cornish-Bowden, A. (2014), Comprensione delle interazioni allosteriche e cooperative negli enzimi. FEBBRAIO J, 281: 621-632. DOI:10.1111/febs.12469</li>
	<li>Alberts et al., 6a edizione; pagine 152-153</li>
	<li>Lehninger Principi di Biochimica, 5a edizione, pagine 162,165</li>
</ol>

transizioni allosteriche cooperazioni

Le transizioni allosteriche cooperative possono verificarsi nelle proteine multimeriche, dove ciascuna subunità della proteina ha il proprio sito di legame del ligando. Quando un ligando si lega a una qualsiasi di queste subunità, innesca un cambiamento conformazionale che influenza i siti di legame nelle altre subunità; questo può cambiare l'affinità degli altri siti per i rispettivi ligandi. La capacità della proteina di modificare la forma del suo sito di legame è attribuita alla presenza di un mix di segmenti flessibili e stabili nella struttura. Una molecola che innesca questo cambiamento è nota come modulatrice.

Per spiegare la cooperatività nelle proteine multimeriche vengono spesso utilizzati due modelli: il modello concertato e quello sequenziale. Il modello concertato, noto anche come modello tutto o niente, ipotizza che tutte le subunità di una proteina multimerica passino simultaneamente dalla conformazione “on” a quella “off”. Nella forma “on”, i siti di legame hanno un’elevata affinità per i rispettivi ligandi, mentre nella forma “off”, i siti di legame hanno una bassa affinità. Quando un ligando si lega a una qualsiasi delle subunità, promuove la conversione nella forma ad alta affinità, modificando contemporaneamente la conformazione di tutti gli altri siti di legame della proteina. Sebbene un ligando possa legarsi a entrambe le forme, è più facile che si leghi quando si trova nella forma ad alta affinità.

Il modello sequenziale presuppone che ciascuna subunità di una proteina multimerica possa esistere indipendentemente in una conformazione “on” o “off”, ovvero nella forma a bassa o alta affinità, indipendentemente dallo stato delle altre subunità. Il legame di un ligando a una subunità modifica l'equilibrio tra la forma a bassa e quella ad alta affinità, così che è più probabile che la subunità sia in forma ad alta affinità. Inoltre, il legame di un ligando su una subunità sposta l'equilibrio per le altre subunità della proteina. Ciò aumenta la probabilità che una volta legato un ligando, un altro ligando si leghi a una subunità diversa. Questa cooperatività aumenta la sensibilità della proteina alla concentrazione del ligando. Il legame del ligando in un singolo sito può modificare l'affinità sull'intera molecola proteica, consentendo così una risposta rapida a basse concentrazioni.

Transizioni Allosteriche Cooperazioni

Le transizioni allosteriche cooperative possono verificarsi nelle proteine multimeriche, dove ogni subunità della proteina ha il proprio sito di legame del ligando. Quando un ligando ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Protein Function

Funzione proteica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

Ligand Binding Sites in Proteins

Ligand binding sites are specific parts of a protein where a ligand can attach. A ligand is a molecule that binds to another molecule, often to help start or change a biological process. These sites matter because the shape and chemistry of the protein help determine which ligands can fit and bind. Proteins do not bind every ligand in the same way. The binding site provides a matching surface that supports a close interaction. In many cases, this interaction is important for how cells respond...

protein-protein interfaces

Protein Binding Surfaces and Contacts

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conserved binding sites

Conserved Binding Sites in Protein Families

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cofactors and coenzymes

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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

Protein Kinases and Phosphatases in Cell Control

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gtpases and their regulation

GTPase Molecular Switches and Control

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covalently linked protein regulators

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protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

Modular Protein Complexes in Cells

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mechanical protein function

Proteins That Generate Cell Movement

Mechanical proteins help cells and tissues move. They turn chemical energy into force and motion. This process is important in many biological systems. These proteins are also called motor proteins. They interact with cell structures and can produce directed movement. In muscle cells, they support contraction. In other cells, they help with transport and shape changes. Mechanical protein function is a key part of how living systems work. It links protein activity to movement at the cellular...

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

Protein interaction networks show how proteins work together inside a cell. These networks help scientists see which proteins connect with each other and how those links support cell activity. Researchers often use online tools to build and study these networks. The transcript points to IntAct and STRING as examples of resources that can help predict and organize protein interactions. These tools make it easier to compare protein links and look for patterns in the network. Protein networks...

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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Allosteric Changes in Protein Shape

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