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

Muchas proteínas tienen múltiples subunidades, donde cada subunidad contiene un sitio de unión al ligando separado.
Cuando una molécula, conocida como modulador, se une a una de las subunidades, desencadena un cambio conformacional en los sitios de unión de las otras subunidades, cambiando su afinidad por sus respectivos ligandos. A esto se le llama transición alostérica cooperativa y puede explicarse mediante varios modelos teóricos.
El modelo concertado o "todo o nada" supone que todas las subunidades existen juntas en una conformación "apagada" o "encendida".
La unión puede ocurrir en cualquiera de las formas, sin embargo, el estado "encendido" tiene una mayor afinidad por el ligando que el estado "apagado". Cuando un ligando se une a cualquiera de las subunidades, promueve la transformación simultánea de todos los sitios de unión a la forma de alta afinidad.
La cooperatividad también puede explicarse por el modelo secuencial, que supone que cada subunidad puede existir independientemente en un estado de alta o baja afinidad, pero es más probable que esté en el estado de alta afinidad cuando el ligando está unido a cualquiera de las subunidades. 
Los sitios de unión de las proteínas alostéricas suelen ser una mezcla de segmentos flexibles y fijos de la cadena de aminoácidos. Cuando un ligando se une, estas partes inestables se estabilizan en una conformación particular, y esto afecta la forma de los sitios de unión en las otras subunidades. 
La hemoglobina es un ejemplo de una proteína tetrámera que experimenta una transición alostérica cooperativa cuando el oxígeno se une.
Cada subunidad de la hemoglobina tiene un solo sitio de unión. Cuando una molécula de oxígeno se une a una sola subunidad, la cooperatividad aumenta la afinidad por el oxígeno en los sitios de unión restantes, lo que facilita que el oxígeno se una a una molécula de hemoglobina que ya tiene oxígeno unido a ella.

<ol>
	<li>Cornish‐Bowden, A. (2014), Comprensión de las interacciones alostéricas y cooperativas en las enzimas. FEBS J, 281: 621-632. doi:10.1111/febs.12469</li>
	<li>Alberts et al., 6ª edición; páginas 152-153</li>
	<li>Principios de Bioquímica de Lehninger, 5ª edición, páginas 162,165</li>
</ol>

transiciones alostéricas cooperativas

Pueden ocurrir transiciones alostéricas cooperativas en proteínas multiméricas, donde cada subunidad de la proteína tiene su propio sitio de unión al ligando. Cuando un ligando se une a cualquiera de estas subunidades, desencadena un cambio conformacional que afecta a los sitios de unión en las otras subunidades, esto puede cambiar la afinidad de los otros sitios por sus respectivos ligandos. La capacidad de la proteína para cambiar la forma de su sitio de unión se atribuye a la presencia de una mezcla de segmentos flexibles y estables en la estructura. Una molécula que desencadena este cambio se conoce como modulador.

A menudo se utilizan dos modelos para explicar la cooperatividad en proteínas multiméricas: el modelo concertado y el secuencial. El modelo concertado, también conocido como modelo de todo o nada, plantea la hipótesis de que todas las subunidades de una proteína multimérica cambian simultáneamente entre las conformaciones "encendido" y "apagado". En la forma "activada", los sitios de unión tienen una alta afinidad por sus respectivos ligandos, y en la forma "apagada", los sitios de unión tienen una baja afinidad. Cuando un ligando se une a cualquiera de las subunidades, promueve la conversión a la forma de alta afinidad, cambiando simultáneamente la conformación de todos los demás sitios de unión de la proteína. Aunque un ligando puede unirse a cualquier forma, le resulta más fácil unirse cuando está en la forma de alta afinidad.

El modelo secuencial supone que cada subunidad de una proteína multimérica puede existir independientemente en una conformación "encendida" o "apagada", es decir, en la forma de baja o alta afinidad, independientemente del estado de las otras subunidades. La unión de un ligando a una subunidad cambia el equilibrio entre las formas de baja y alta afinidad, de modo que es más probable que la subunidad esté en la forma de alta afinidad. Además, la unión de un ligando a una subunidad cambia el equilibrio de las otras subunidades de la proteína. Esto aumenta la probabilidad de que una vez que se une un ligando, otro ligando se una a una subunidad diferente. Esta cooperatividad aumenta la sensibilidad de la proteína a la concentración de ligando. La unión de un ligando a un solo sitio puede cambiar la afinidad en toda la molécula de proteína, permitiendo así una respuesta rápida en concentraciones bajas.

Transiciones alostéricas cooperativas

Las transiciones alostéricas cooperativas pueden ocurrir en proteínas multiméricas, donde cada subunidad de la proteína tiene su propio sitio de unión al ligando. Cuando un ligando ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Protein Function

Función proteica

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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

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protein-protein interfaces

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conserved binding sites

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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

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covalently linked protein regulators

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protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

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mechanical protein function

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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

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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-LS1-2

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HS-LS1-3

Allosteric Changes in Protein Shape

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