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

كثير من البروتينات بها وحدات فرعية متعددة حيث تحتوي كل وحدة فرعية على موقع ربط منفصل لليجاند عندما يرتبط جزيء يعرف باسم المعدّلات بأحد الوحدات الفرعية،فهو يحفز تغيير فى التشكٌل مواقع الربط الخاصة بالوحدات الفرعية الأخرى،مغيرة بذلك قابلية تقاربهم لليجاند الخاص بهم. وهذا ما يسمى تحوُل تعاونى تفارغى ويمكن شرحه بواسطة العديد من النماذج النظرية. الجميع أو الكل أو لا شيء يفترض أن كافة الوحدات الفرعية موجودة معًبعضها في تشكّل ايقاف او تشغيل.يمكن أن يحدث الربط في أي من الشكلين. ومع ذلك،فإن حالة التشغيل بها تقارب عالى للليجاند عن حالة الإيقاف عندما يرتبط الليجاند عند أي من الوحدات الفرعية،يقوم بتعزيزالتحويل التلقائى لجميع مواقع الربط إلى نموذج عالى التقارب. بشكل تعاوني يمكن شرحه ايضا بالنموذج التسلسلي،الذي يفرض أن كل وحدة فرعية يمكنها أن تتواجد بشكل مستقل في حالة تقارب مرتفعة أو منخفضة ولكن من المرجح أن تكون في حالة التقارب المرتفع عندما يرتبط الليجاند بأى من الوحدات الفرعية.مواقع الربط لـبروتينات التفارغية عادة ما تكون مزيجاًمن المقاطع المرنة والثابتة من سلسلة حمض الأمينى. عندما يتربط الليجاند،هذه الأجزاء غير المستقرة تكون قد أستقرت فى تشكّل خاص وهذا يؤثر على شكل مواقع الربط على الوحدات الفرعية الأخرى. الهيموجلوبين مثال على بروتين رباعي الأوجه والذى يخضع لتحول تعاونى تفارغى عندما يرتبط الأكسجين.كل وحدة فرعية من الهيموجلوبين تحتوي على موقع ربط واحد عندما يرتبط جزيء واحد من الأكسجين بوحدة فرعية واحدة،بشكل تعاوني يزيد قابلية تجاذب الأكسجين الموجود على مواقع الروابط المتبقية،جاعلا ذلك اسهل للأكسجين كى يرتبط بجزيء الهيموجلوبين الذى به أكسجين مرتبط به بالفعل.

<ol>
	<li>كورنيش بودين ، أ. (2014) ، فهم التفاعلات الخيفية والتعاونية في الإنزيمات. FEBS J ، 281: 621-632. دوي: 10.1111 / فبراير 12469</li>
	<li>ألبرتس وآخرون ، الطبعة السادسة ؛ الصفحات 152-153</li>
	<li>مبادئ Lehninger للكيمياء الحيوية ، الطبعة الخامسة ، الصفحات 162،165</li>
</ol>

التحولات التعاونية الخيفية

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يمكن أن تحدث التحولات اللوستيرية التعاونية في البروتينات متعددة القسيمات، حيث يكون لكل وحدة فرعية من البروتين موقع ربط خاص بها. عندما ترتبط الربيطة بأي من هذه الوحدات الفرعية، فإنها تؤدي إلى تغيير تكويني يؤثر على مواقع الارتباط في الوحدات الفرعية الأخرى؛ يمكن أن يؤدي هذا إلى تغيير تقارب المواقع الأخرى مع الروابط الخاصة بها. تُعزى قدرة البروتين على تغيير شكل موقع الارتباط الخاص به إلى وجود مزيج من الأجزاء المرنة والمستقرة في البنية. يُعرف الجزيء الذي يؤدي إلى هذا التغيير باسم المغير.

غالبًا ما يتم استخدام نموذجين لشرح التعاون في البروتينات متعددة القسيمات: النموذج المنسق والنموذج المتسلسل. يفترض النموذج المنسق، المعروف أيضًا باسم نموذج الكل أو لا شيء، أن جميع الوحدات الفرعية للبروتين متعدد القسيمات تتحول في وقت واحد بين مطابقتي "التشغيل" و"الإيقاف". في النموذج "on"، تتمتع مواقع الربط بتقارب عالٍ للروابط الخاصة بها، وفي النموذج "off"، تتمتع مواقع الربط بتقارب منخفض. عندما ترتبط الربيطة بأي من الوحدات الفرعية، فإنها تعزز التحويل إلى الشكل عالي الألفة، مما يؤدي في الوقت نفسه إلى تغيير شكل جميع مواقع الارتباط الأخرى للبروتين. على الرغم من أن المركب يمكنه الارتباط بأي من النموذجين، إلا أنه من الأسهل الارتباط به عندما يكون في النموذج عالي الألفة.

يفترض النموذج التسلسلي أن كل وحدة فرعية من البروتين متعدد القسيمات يمكن أن توجد بشكل مستقل في شكل "تشغيل" أو "إيقاف"، أي في شكل منخفض أو عالي الألفة، بغض النظر عن حالة الوحدات الفرعية الأخرى. يؤدي ربط الروابط بوحدة فرعية إلى تغيير التوازن بين الأشكال المنخفضة والعالية الألفة بحيث يكون من الأرجح أن تكون الوحدة الفرعية في شكل عالي الألفة. بالإضافة إلى ذلك، فإن ارتباط الربيطة على وحدة فرعية واحدة يؤدي إلى تغيير التوازن للوحدات الفرعية الأخرى في البروتين. وهذا يزيد من احتمالية أنه بمجرد ربط رابطة واحدة، سترتبط رابطة أخرى بوحدة فرعية مختلفة. يزيد هذا التعاون من حساسية البروتين لتركيز الربيطة. يمكن لربط الروابط في موقع واحد أن يغير الألفة على جزيء البروتين بأكمله، مما يتيح الاستجابة السريعة بتركيزات منخفضة.

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يمكن أن تحدث التحولات الخيفية التعاونية في البروتينات متعددة الأشكال ، حيث يكون لكل وحدة فرعية من البروتين موقع ربط الترابط الخاص بها. عندما يجند ...

Education

JoVE Core

Cell Biology

بيولوجيا الخلية

Unit 1

الوحدة الأولى

Protein Function

وظيفة البروتين

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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

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HS-LS1-2

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HS-LS1-3

Allosteric Changes in Protein Shape

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