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

多くのタンパク質には複数のサブユニットがあり、各サブユニットには個別のリガンド結合部位が含まれています。
モジュレーターと呼ばれる分子がサブユニットの1つに結合すると、他のサブユニットの結合部位にコンフォメーション変化が起こり、それぞれのリガンドに対する親和性が変化します。これは協調アロステリック転移と呼ばれ、いくつかの理論モデルで説明できます。
協調モデルまたは「オール・オア・ナッシング」モデルは、すべてのサブユニットが「オフ」または「オン」のコンフォメーションで一緒に存在すると仮定します。
結合はどちらの形式でも発生する可能性がありますが、「オン」状態は「オフ」状態よりもリガンドに対する親和性が高くなります。リガンドがいずれかのサブユニットで結合すると、すべての結合部位が同時に高親和性形態への変換を促進します。
協調性は、各サブユニットが高親和性または低親和性状態で独立して存在できると仮定するシーケンシャルモデルによっても説明できますが、リガンドがサブユニットのいずれかに結合している場合は高親和性状態になる可能性が高くなります。 
アロステリックタンパク質の結合部位は、通常、アミノ酸鎖の柔軟なセグメントと固定されたセグメントの混合物です。リガンドが結合すると、これらの不安定な部分は特定のコンフォメーションで安定化され、これが他のサブユニットの結合部位の形状に影響を与えます。 
ヘモグロビンは、酸素が結合するときに協調的なアロステリック遷移を起こす四量体タンパク質の一例です。
ヘモグロビンの各サブユニットは単一の結合部位を有する。1分子の酸素が1つのサブユニットに結合すると、協力性により残りの結合部位の酸素に対する親和性が高まり、すでに酸素が結合しているヘモグロビン分子に酸素が結合しやすくなります。

<ol>
	<li>Cornish-Bowden、A.(2014)、酵素におけるアロステリックおよび協力的相互作用の理解。FEBS J、281:621-632。DOI:10.1111/febs.12469</li>
	<li>Alberts et al., 6th edition; pages 152-153</li> (英語)
	<li>Lehninger Principles of Biochemistry、第5版、162,165ページ</li>
</ol>

協調的アロステリックトランジション

協調的なアロステリック転移は多量体タンパク質で発生する可能性があり、タンパク質の各サブユニットには独自のリガンド結合部位があります。リガンドがこれらのサブユニットのいずれかに結合すると、他のサブユニットの結合部位に影響を与える構造変化が引き起こされます。これにより、他の部位のそれぞれのリガンドに対する親和性が変化する可能性があります。結合部位の形状を変化させるタンパク質の能力は、構造内に柔軟なセグメントと安定なセグメントが混在していることに起因すると考えられます。 この変化を引き起こす分子はモジュレーターとして知られています。

多量体タンパク質の協同性を説明するために、協奏モデルと逐次モデルという 2 つのモデルがよく使用されます。 all-or-none モデルとしても知られる協調モデルは、多量体タンパク質のすべてのサブユニットが「オン」構造と「オフ」構造の間で同時に切り替わるという仮説を立てています。 「オン」型では、結合部位はそれぞれのリガンドに対して高い親和性を持ち、「オフ」型では、結合部位は低い親和性を持ちます。 リガンドがサブユニットのいずれかに結合すると、高親和性形態への変換が促進され、同時にタンパク質の他のすべての結合部位の立体構造が変化します。 リガンドはどちらの形態にも結合できますが、高親和性形態の方が結合しやすくなります。

逐次モデルでは、多量体タンパク質の各サブユニットが、他のサブユニットの状態に関係なく、「オン」または「オフ」立体構造、つまり低親和性または高親和性のいずれかの形態で独立して存在できると想定しています。 リガンドがサブユニットに結合すると、低親和性形態と高親和性形態の間の平衡が変化し、サブユニットが高親和性形態になる可能性が高くなります。さらに、1つのサブユニットにリガンドが結合すると、タンパク質内の他のサブユニットの平衡が変化します。 これにより、1 つのリガンドが結合すると、別のリガンドが別のサブユニットに結合する可能性が高くなります。 この協同性により、リガンド濃度に対するタンパク質の感受性が高まります。 単一部位に結合するリガンドはタンパク質分子全体の親和性を変化させることができるため、低濃度での迅速な応答が可能になります。

協働的なアロステリックトランジションは、タンパク質の各サブユニットが独自のリガンド結合部位を持つ多量体タンパク質で発生する可能性があります。リガンドが...

Education

JoVE Core

Cell Biology

細胞生物学

Unit 1

ユニット1

Protein Function

タンパク質の機能

KEY TERMS AND CONCEPTS

主要用語と概念

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 細胞生物学は、複雑な細胞プロセスを、わかりやすく包括的なアニメーション ビデオ レッスンで説明します。このコレクションは、細胞小器官や膜、細胞輸送、細胞のエネルギー学など、細胞の必須コンポーネントと機能に焦点を当てています。これは、実際の研究実験における細胞生物学の応用を実証する科学者による実際のビデオによって補足されています。

Characteristics of Life

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Protein and Protein Structures

Conjugated Proteins

Proteins: From Genes to Degradation

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Covalently Linked Protein Regulators

Protein Complexes with Interchangeable Parts

Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

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The Parasympathetic Nervous System

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The Sympathetic Nervous System

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Physiology of the Circulatory System

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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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Negative and Positive Feedback

Homeostatic Imbalance

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pH Homeostasis

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Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

HS-LS1-3

Allosteric Changes in Protein Shape

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