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

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

Energy and Catalysis

Energia e Catalisi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

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oxidation-and-reduction-of-organic-molecules

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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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How Proteins Shift Shape Together | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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

Ribozymes

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Prokaryotic Cells

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Cytoplasm

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The Nucleus

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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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