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

Many proteins have multiple subunits, where each subunit contains a separate ligand binding site.
When a molecule, known as a modulator, binds to one of the subunits it triggers a conformational change in the binding sites of the other subunits changing their affinity for their respective ligands. This is called a cooperative allosteric transition and can be explained by several theoretical models.
The concerted or &#8220;all-or-none&#8221; model assumes that all of the subunits exist together in either an &#8220;off&#8221; or &#8220;on&#8221; conformation.
Binding can occur in either form, however, the &#8220;on&#8221; state has a higher affinity for the ligand than the &#8220;off&#8221; state. When a ligand binds at any of the subunits, it promotes the simultaneous transformation of all of the binding sites to the high-affinity form.
Cooperativity can also be explained by the sequential model, which assumes that each subunit can exist independently in a high or low-affinity state, but is more likely to be in the high-affinity state when the ligand is bound to any of the subunits.&#160;
The binding sites of allosteric proteins are usually a mix of flexible and fixed segments of the amino acid chain. When a ligand binds, these unstable parts are stabilized in a particular conformation, and this affects the shape of the binding sites on the other subunits.&#160;
Hemoglobin is an example of a tetrameric protein that undergoes a cooperative allosteric transition when oxygen binds.
Each subunit of hemoglobin has a single binding site. When one molecule of oxygen binds to a single subunit, cooperativity increases the affinity for oxygen on the remaining binding sites making it easier for oxygen to bind to a molecule of hemoglobin that already has oxygen bound to it.&#160;

cooperative allosteric transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the structure.&#160; A molecule that triggers this change is known as a modulator.
Two models are often used to explain cooperativity in multimeric proteins: the concerted and the sequential model. The concerted model, also known as the all-or-none model, hypothesizes that all the subunits of a multimeric protein&#160; switch simultaneously between the &#8220;on&#8221; and &#8220;off&#8221; conformations. In the &#8220;on&#8221; form, the binding sites have a high affinity for their respective ligands, and in the &#8220;off&#8221; form, the binding sites have a low affinity. When a ligand binds to any one of the subunits, it promotes the conversion to the high-affinity form, simultaneously changing the conformation of all other binding sites of the protein. Although a ligand can bind to either form, it is easier for it to bind when in the high-affinity form.
The sequential model assumes that each subunit of a multimeric protein can exist independently in an &#8220;on&#8221; or &#8220;off&#8221; conformation, that is in either the low or high-affinity form, regardless of the state of the other subunits.&#160; Binding of a ligand to a subunit changes the equilibrium between the low and high-affinity forms such that it is more likely for the subunit to be in high-affinity form.&#160; Additionally, a ligand binding on one subunit shifts the equilibrium for the other subunits in the protein. This increases the likelihood that once one ligand is bound, another ligand will bind to a different subunit.&#160; This cooperativity increases the sensitivity of the protein to ligand concentration. A ligand binding at a single site can change the affinity on the entire protein molecule, thereby enabling a rapid response at low concentrations.

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand ...

Education

JoVE Core

Cell Biology

Unit 1

Protein Function

KEY TERMS AND CONCEPTS

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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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

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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

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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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