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

Birçok proteinde, her birinde ayrı bir ligand bağlanma yeri bulunan alt birimler vardır. Modülatör olarak adlandırılan bir molekül, alt birimlerden birine bağlandığında, diğer alt birimlerin bağlanma yerlerinde konformasyonel bir değişikliği tetikleyerek, bunların ilgili ligandları için afinitesini değiştirir. Bu, işbirlikçi allosterik geçiş olarak adlandırılır ve birçok teorik modelle açıklanabilir.Toplu düzenlenme veya ya hep ya hiç"modeli, tüm alt birimlerin hep birlikte kapalı veya açık yapıda olduğunu varsayar. Bağlanma her iki şekilde de gerçekleşebilir. Bununla birlikte, açık durumu kapalı duruma göre ligand için daha yüksek bir afiniteye sahiptir.Bir ligand, alt birimlerin herhangi birine bağlandığında, tüm bağlanma yerlerinin aynı anda yüksek afinite formuna dönüşmesini sağlar. İşbirliği, her bir alt birimin bağımsız olarak yüksek veya düşük afinite durumunda olabileceğini, ancak ligand alt birimlerden birine bağlandığında yüksek afinite durumunda olma olasılığının daha yüksek olduğunu varsayan, sırasal düzenleme modeli ile de açıklanabilir. Allosterik proteinlerin bağlanma yerleri genellikle, amino asit zincirinin esnek ve sabit segmentlerinin bir karışımıdır.Bir ligand bağlandığında, bu kararsız parçalar belirli bir konformasyonda kararlılaşır. Ve bu, diğer alt birimlerdeki bağlanma yerlerinin şeklini etkiler. Hemoglobin, oksijen bağlandığında işbirlikçi bir allosterik geçişe uğrayan, bir tetramerik protein örneğidir.Her hemoglobinin alt biriminin tek bir bağlanma yeri vardır. Bir oksijen molekülü tek bir alt birime bağlandığında, işbirliği, geri kalan bağlanma yerlerindeki oksijene olan afiniteyi arttırır;bu da oksijenin zaten kendisine bağlı oksijen bulunan bir hemoglobin molekülüne bağlanmasını kolaylaştırır.

<ol>
	<li>Cornish-Bowden, A. (2014), Enzimlerde allosterik ve işbirlikçi etkileşimleri anlamak. ŞUBAT J, 281: 621-632. doi:10.1111/şubat.12469</li>
	<li>Alberts ve diğerleri, 6. baskı; sayfa 152-153</li>
	<li>Lehninger Biyokimya İlkeleri, 5. baskı, sayfa 162,165</li>
</ol>

İşbirlikçi allosterik geçişler

Proteinin her alt biriminin kendi ligand bağlama bölgesine sahip olduğu multimerik proteinlerde işbirliğiyle allosterik geçişler meydana gelebilir. Bir ligand bu alt birimlerden herhangi birine bağlandığında, diğer alt birimlerdeki bağlanma bölgelerini etkileyen konformasyonel bir değişikliği tetikler; bu, diğer bölgelerin ilgili ligandlara olan afinitesini değiştirebilir. Proteinin bağlanma bölgesinin şeklini değiştirme yeteneği, yapıdaki esnek ve stabil segmentlerin bir karışımının varlığına atfedilir. Bu değişikliği tetikleyen moleküle modülatör adı verilir. Multimerik proteinlerdeki işbirliğini açıklamak için sıklıkla iki model kullanılır: tek adımlı ve sıralı model. Ya hep ya hiç modeli olarak da bilinen tek adımlı model, multimerik bir proteinin tüm alt birimlerinin aynı anda "açık" ve "kapalı" konformasyonlar arasında geçiş yaptığını varsayar. "Açık" formda bağlanma bölgeleri ilgili ligandlara karşı yüksek afiniteye sahiptir ve "kapalı" formda bağlanma bölgeleri düşük afiniteye sahiptir. Bir ligand alt birimlerden herhangi birine bağlandığında, yüksek afiniteli forma dönüşümü teşvik eder ve aynı anda proteinin diğer tüm bağlanma bölgelerinin konformasyonunu değiştirir. Bir ligand her iki forma da bağlanabilmesine rağmen, yüksek afiniteli formda bağlanması daha kolaydır. Sıralı model, multimerik bir proteinin her bir alt biriminin, diğer alt birimlerin durumuna bakılmaksızın bağımsız olarak "açık" veya "kapalı" konformasyonda, yani düşük veya yüksek afiniteli formda var olabileceğini varsayar. Bir ligandın bir alt birime bağlanması, düşük ve yüksek afiniteli formlar arasındaki dengeyi değiştirerek alt birimin yüksek afiniteli formda olma olasılığını artırır. Ek olarak, bir alt birime bağlanan bir ligand, proteindeki diğer alt birimlerin dengesini değiştirir. Bu, bir ligand bağlandığında başka bir ligandın farklı bir alt birime bağlanma olasılığını artırır. Bu işbirliği, proteinin ligand konsantrasyonuna duyarlılığını arttırır. Tek bir bölgedeki ligand bağlanması, tüm protein molekülü üzerindeki afiniteyi değiştirebilir, böylece düşük konsantrasyonlarda hızlı bir tepkiye olanak sağlar.

İşbirlikçi Allosterik Geçişler

Kooperatif allosterik geçişler, proteinin her bir alt biriminin kendi ligand bağlanma bölgesine sahip olduğu multimerik proteinlerde meydana gelebilir. Bir ligand ne zaman ...

Education

JoVE Core

Cell Biology

Hücre Biyolojisi

Unit 1

Ünite 1

Protein Function

Protein Fonksiyonu

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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

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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

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

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HS-LS1-2

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HS-LS1-3

Allosteric Changes in Protein Shape

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