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

Wiele białek ma wiele podjednostek, z których każda zawiera oddzielne miejsce wiązania liganda.
Kiedy cząsteczka, znana jako modulator, wiąże się z jedną z podjednostek, wyzwala zmianę konformacyjną w miejscach wiązania innych podjednostek, zmieniając ich powinowactwo do odpowiednich ligandów. Nazywa się to kooperatywnym przejściem allosterycznym i można je wyjaśnić za pomocą kilku modeli teoretycznych.
Model uzgodniony lub "wszystko albo nic" zakłada, że wszystkie podjednostki istnieją razem w konformacji "wyłączonej" lub "włączonej".
Wiązanie może wystąpić w dowolnej formie, jednak stan "włączony" ma większe powinowactwo do liganda niż stan "wyłączony". Kiedy ligand wiąże się w którejkolwiek z podjednostek, sprzyja jednoczesnej transformacji wszystkich miejsc wiązania do formy o wysokim powinowactwie.
Kooperatywność można również wyjaśnić za pomocą modelu sekwencyjnego, który zakłada, że każda podjednostka może istnieć niezależnie w stanie wysokiego lub niskiego powinowactwa, ale bardziej prawdopodobne jest, że będzie w stanie wysokiego powinowactwa, gdy ligand jest związany z którąkolwiek z podjednostek. 
Miejsca wiązania białek allosterycznych są zwykle mieszanką elastycznych i stałych segmentów łańcucha aminokwasowego. Kiedy ligand się wiąże, te niestabilne części są stabilizowane w określonej konformacji, a to wpływa na kształt miejsc wiązania na innych podjednostkach. 
Hemoglobina jest przykładem białka tetramerycznego, które ulega kooperatywnemu przejściu allosterycznym, gdy wiąże się tlen.
Każda podjednostka hemoglobiny ma pojedyncze miejsce wiązania. Kiedy jedna cząsteczka tlenu wiąże się z pojedynczą podjednostką, kooperatywność zwiększa powinowactwo do tlenu w pozostałych miejscach wiązania, ułatwiając tlenowi wiązanie się z cząsteczką hemoglobiny, która jest już związana z tlenem.

<ol>
	<li>Cornish-Bowden, A. (2014), Zrozumienie interakcji allosterycznych i kooperacyjnych w enzymach. LUTY J, 281: 621-632. doi:10.1111/febs.12469</li>
	<li>Alberts et al., wydanie 6; strony 152-153</li>
	<li>Lehninger Zasady biochemii, wydanie 5, strony 162,165</li>
</ol>

kooperacyjne przejścia allosteryczne

Przejście allosteryczne może zachodzić w białkach multimerycznych, gdzie każda podjednostka białka ma swoje własne miejsce wiązania liganda. Kiedy ligand wiąże się z którąkolwiek z tych podjednostek, wyzwala zmianę allosteryczną, która wpływa na miejsca wiązania w innych podjednostkach; może to zmienić powinowactwo innych miejsc dla ich odpowiednich ligandów. Zdolność białka do zmiany kształtu miejsca wiązania przypisuje się obecności w strukturze mieszanki elastycznych i stabilnych segmentów. Cząsteczka, która wyzwala tę zmianę, nazywana jest modulatorem. Do wyjaśnienia kooperatywności białek multimerycznych często stosuje się dwa modele: model skoncentrowany i model sekwencyjny. Model skoncentrowany, znany również jako model „wszystko albo nic”, zakłada, że wszystkie podjednostki multimerycznego białka przełączają się jednocześnie między konformacją „włączoną” i „wyłączoną”. W formie „włączonej” miejsca wiązania mają wysokie powinowactwo do odpowiednich ligandów, a w formie „wyłączonej” miejsca wiązania mają niskie powinowactwo. Kiedy ligand wiąże się z którąkolwiek z podjednostek, sprzyja konwersji do postaci o wysokim powinowactwie, jednocześnie zmieniając konformację wszystkich innych miejsc wiązania białka. Chociaż ligand może wiązać się z dowolną formą, łatwiej jest mu się związać, gdy jest w formie o wysokim powinowactwie. Model sekwencyjny zakłada, że każda podjednostka multimerycznego białka może istnieć niezależnie w konformacji „włączonej” lub „wyłączonej”, czyli w formie o niskim lub wysokim powinowactwie, niezależnie od stanu pozostałych podjednostek. Wiązanie ligandu z podjednostką zmienia równowagę pomiędzy formami o niskim i wysokim powinowactwie, tak że jest bardziej prawdopodobne, że podjednostka będzie w postaci o wysokim powinowactwie. Dodatkowo wiązanie ligandu z jedną podjednostką przesuwa równowagę pozostałych podjednostek białka. Zwiększa to prawdopodobieństwo, że po związaniu jednego liganda inny ligand zwiąże się z inną podjednostką. Ta kooperatywność zwiększa wrażliwość białka na stężenie ligandu. Wiązanie ligandu w jednym miejscu może zmienić powinowactwo całej cząsteczki białka, umożliwiając w ten sposób szybką reakcję przy niskich stężeniach.

Kooperacyjne przejścia allosteryczne

Kooperacyjne przejścia allosteryczne mogą zachodzić w białkach multimerycznych, w których każda podjednostka białka ma swoje własne miejsce wiązania ligandu. Kiedy ligand ...

Education

JoVE Core

Cell Biology

Biologia komórki

Unit 1

Jednostka 1

Protein Function

Funkcja białka

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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

Conserved binding sites are regions on proteins that stay similar across related proteins. These shared areas often help proteins interact with the same molecules. For this reason, they are useful clues when comparing protein families. A conserved site can help identify where a protein binds. It can also show which parts of the protein are important for function. When the same pattern appears in several proteins, it suggests that the site has been kept through evolution. Scientists look at...

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

Protein kinases and phosphatases help control how proteins work in cells. Kinases add phosphate groups to proteins. Phosphatases remove those phosphate groups. This phosphorylation and dephosphorylation process can change a protein’s shape and activity. It is one way cells turn protein function on or off at the right time. These changes also help cells respond to signals and manage many cell activities. Together, protein kinases and phosphatases keep cellular signaling balanced. When one adds...

gtpases and their regulation

GTPase Molecular Switches and Control

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covalently linked protein regulators

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Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves. Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function. Covalently linked...

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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HS-LS1-3

Allosteric Changes in Protein Shape

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