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

Muitas proteínas têm múltiplas subunidades onde cada subunidade contém um sítio de ligação do ligante. Quando uma molécula conhecida como modulador se liga a uma das subunidades, ele dispara uma mudança conformacional nos sítios de ligação das outras subunidades, mudando sua afinidade para seus respetivos ligantes. Isto é chamado uma transição alostérica cooperativa e pode ser explicado por vários modelos teóricos.O modelo concertado ou on ligado ou off desligado supõe que todas as subunidades existem junto em um on ligado ou off desligado na confirmação. A ligação pode ocorrer em qualquer uma das formas. No entanto, o estado on ligado tem uma afinidade mais elevada para o ligante do que o estado off desligado.Quando um ligante se liga em qualquer uma das subunidades, promove a transformação simultânea de todos os sítios de ligação à forma de alta afinidade. Cooperativamente, também pode ser explicado pelo modelo sequencial, que assume que cada subunidade pode existir independentemente em um estado de alta ou baixa afinidade 00:01:03.780 00:01:06.600 mas é mais provável estar no estado de alta afinidade quando o ligante está ligado a qualquer uma das subunidades. Os sítios de ligação de proteínas alostéricas são geralmente uma mistura de segmentos flexíveis e fixos da cadeia de aminoácidos.Quando um ligante se liga, estas partes instáveis são estabilizadas em uma conformação particular. E isto afeta a forma do sítio da ligação nas outras subunidades. A hemoglobina é um exemplo de uma proteína tetramérica que sofre uma transição alostérica cooperativa quando o oxigénio liga.Cada subunidade de hemoglobina tem um único sítio de ligação. Quando uma molécula de oxigénio se liga a uma única subunidade, aumenta cooperativamente a afinidade para o oxigénio nos sítios de ligação restantes, tornando mais fácil para o oxigénio se ligar 00:01-52.110 00:01:57.500 a uma molécula de hemoglobina que já tem oxigénio ligado a ela.

<ol>
	<li>Cornish-Bowden, A. (2014), Compreendendo as interações alostéricas e cooperativas em enzimas. FEBS J, 281: 621-632. DOI:10.1111/fev.12469</li>
	<li>Alberts et al., 6ª edição; páginas 152-153</li>
	<li>Princípios de Bioquímica de Lehninger, 5ª edição, páginas 162,165</li>
</ol>

transições alostéricas cooperativas

Transições alostéricas cooperativas podem ocorrer em proteínas multiméricas, onde cada subunidade da proteína tem seu próprio sítio de ligação do ligante. Quando um ligante se liga a qualquer uma dessas subunidades, desencadeia uma mudança conformacional que afeta os sítios de ligação nas outras subunidades; isso pode alterar a afinidade dos outros sítios para seus respectivos ligantes. A capacidade da proteína de alterar a forma do seu sítio de ligação é atribuída à presença de uma mistura de segmentos flexíveis e estáveis na estrutura. Uma molécula que desencadeia essa mudança é conhecida como modulador. Dois modelos são frequentemente usados para explicar a cooperatividade em proteínas multiméricas: o modelo concertado e o modelo sequencial. O modelo concertado, também conhecido como modelo tudo ou nada, levanta a hipótese de que todas as subunidades de uma proteína multimérica alternam simultaneamente entre as conformações “ligada” e “desligada”. Na forma “ligada”, os sítios de ligação têm alta afinidade para seus respectivos ligantes, e na forma “desligada”, os sítios de ligação têm baixa afinidade. Quando um ligante se liga a qualquer uma das subunidades, promove a conversão para a forma de alta afinidade, alterando simultaneamente a conformação de todos os outros sítios de ligação da proteína. Embora um ligante possa se ligar a qualquer uma das formas, é mais fácil ligá-lo quando está na forma de alta afinidade. O modelo sequencial assume que cada subunidade de uma proteína multimérica pode existir independentemente em uma conformação “ligada” ou “desligada”, ou seja, na forma de baixa ou alta afinidade, independentemente do estado das outras subunidades. A ligação de um ligante a uma subunidade altera o equilíbrio entre as formas de baixa e alta afinidade, de modo que é mais provável que a subunidade esteja na forma de alta afinidade. Além disso, a ligação de um ligante a uma subunidade altera o equilíbrio das outras subunidades da proteína. Isto aumenta a probabilidade de que, uma vez ligado um ligante, outro ligante se ligue a uma subunidade diferente. Essa cooperatividade aumenta a sensibilidade da proteína à concentração do ligante. A ligação de um ligante em um único local pode alterar a afinidade de toda a molécula de proteína, permitindo assim uma resposta rápida em baixas concentrações.

Transições Alostéricas Cooperativas

Transições alostéricas cooperativas podem ocorrer em proteínas multiméricas, onde cada subunidade da proteína tem seu próprio local de ligação ao ligante. Quando um ligante ...

Education

JoVE Core

Cell Biology

Biologia Celular

Unit 1

Unidade 1

Protein Function

Função Proteica

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

Protein binding surfaces and contacts help proteins recognize and attach to each other. These interfaces are the regions where two proteins meet and interact. They are important for many cell processes and for how proteins work together. A protein-protein interface is not just a random touch point. It is shaped by the three-dimensional form of each protein. The matching surfaces allow a stable interaction to form when the proteins fit together well. Studying these interfaces helps explain how...

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

Enzyme Helpers: Metals and Vitamins

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors. Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These...

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

GTPases are molecular switches that help control cell activity. They bind guanosine triphosphate, or GTP, and can change between active and inactive states. This switch-like behavior makes them important in many cell processes. The protein is active when GTP is bound and inactive when guanosine diphosphate, or GDP, is bound. GTPases can also turn themselves off by breaking down GTP into GDP. This built-in control helps cells regulate when the protein is on or off. Their activity is regulated...

covalently linked protein regulators

Protein Regulation by Covalent Bonds

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

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior. A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change. The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins...

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

cell biology

JoVE Core - Biologia Celular ilustra processos celulares complexos em vídeos de animação fáceis de entender e, ao mesmo tempo, abrangentes. Esta coleção foca nos componentes e funções essenciais das células, incluindo organelas e membranas, transporte celular e energia celular. É complementado por vídeos de Cientistas em ação que demonstram a aplicação da biologia celular em experimentos de pesquisa do mundo real.

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

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HS-LS1-3

Allosteric Changes in Protein Shape

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