Name: modular protein complexes in cells
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 1 min 57 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

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

Les complexes protéiques sont composés de nombreuses protéines liées de manière non-covalente, où chaque composant fournit une fonction différente au complexe. Une ou plusieurs de ces protéines individuelles peuvent être remplacées par des variantes étroitement liées pour créer un complexe alternatif qui est fonctionnellement distinct. À mesure qu'un organisme évolue, le gène d'une protéine bénéfique peut se dupliquer dans le génome.Cette copie dupliquée est libre de subir des mutations sans affecter la fonction de la protéine originale. Ces mutations génèrent des familles de protéines apparentées. C'est l'une des manières pour une cellule de générer un complexe protéique contenant des parties interchangeables.L'ubiquitine ligase SCF est une protéine multimérique composée de cinq sous-unités. Sa fonction est d'attacher des molécules d'ubiquitine pour cibler les protéines, en les marquant pour la dégradation par les enzymes protéolytiques. Une des sous-unités de la protéine, la boite F, qui est responsable de la liaison à la protéine cible, a plusieurs variants qui sont interchangeables.Un changement dans cette sous-unité permet au complexe de marquer différentes protéines pour la dégradation. Saccharomyces cerevisiae, communément connu sous le nom de levure de Baker, possède 11 variants des sous-unités boite F, permettant à la ligase de marquer les protéines impliquées dans divers processus cellulaires. Par exemple, la protéine CDC 4 boite-F cible les régulateurs de cycle cellulaire, tels que SIC 1 et FAR 1, qui inhibent les enzymes qui favorisent le cycle cellulaire.Leur dégradation permet de poursuivre le cycle cellulaire. La variation de la boite F entre les organismes génère des centaines de complexes distincts avec des fonctions similaires mais des cibles différentes.

<ol>
	<li>Alberts et al., 6e édition ; pages 159-160</li>
	<li>Kipreos, E. T. et Pagano, M. (2000). La famille des protéines F-box. Biologie du génome, 1(5), REVIEWS3002. doi :10.1186/gb-2000-1-5-reviews300</li>
</ol>

complexe protéique avec des éléments interchangeables

Des groupes de protéines peuvent former un complexe dans lequel chaque protéine de ce complexe joue un rôle différent dans l’exécution globale de la fonction du complexe. Souvent, certaines des protéines du complexe peuvent être remplacées par une variante étroitement apparentée pour donner un complexe contenant plusieurs des mêmes composants tout en étant fonctionnellement distinct.

L'ubiquitine ligase SCF est un complexe protéique de cinq protéines individuelles. Ce complexe attache l'ubiquitine à d'autres protéines cibles pour les marquer en vue de leur dégradation. Afin de remplir cette fonction, l'une des protéines, la F-box, est responsable de la liaison au substrat, permettant ainsi à une protéine différente du complexe, l'enzyme de conjugaison de l'ubiquitine, d'accéder au substrat et de fixer l'ubiquitine. La protéine F-box possède plusieurs variantes interchangeables afin que le complexe puisse reconnaître différents substrats. De plus, différents organismes peuvent avoir différents ensembles de variantes de protéines F-box. Les humains ont 38 variantes connues, Saccharomyces cerevisiae en a 11, la drosophile en a 22 et C. elegans en a 326. Cette variation permet au complexe de cibler un large spectre de protéines en modifiant un seul de ses composants.

Ces variantes interchangeables sont souvent le résultat d’une duplication génétique. Au cours de l'évolution moléculaire, le gène d'une protéine bénéfique peut parfois se dupliquer lors de la réplication de l'ADN pour des raisons telles que la recombinaison ectopique, le glissement de réplication, l'aneuploïdie, la polyploïdie et la rétrotransposition. Cette copie dupliquée du gène peut en outre subir des mutations tout en étant transférée d'une génération à la suivante, car la mutation n'affecte pas la fonction du gène d'origine. Ces mutations aboutissent à des variantes d'un gène responsable de protéines, comme la F-box, qui sont fonctionnellement similaires mais ont des spécificités de substrat différentes.

Complexe protéique avec des éléments interchangeables

Des groupes de protéines peuvent former un complexe où chaque protéine de ce complexe a un rôle différent dans l’exécution globale de la fonction du complexe. ...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Protein Function

Fonction des protéines

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 recognize different target proteins. This lets one core complex act on many different targets.

This kind of protein complex shows how cells use shared building blocks to create functional variety. By swapping one part, the same basic structure can take on new roles in protein control.

Modular Protein Complexes in Cells

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

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 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 how cells build protein complexes from interchangeable parts, including the SCF ubiquitin ligase and its F-box subunit that determines target specificity.

Modular Protein Complexes in Cells | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Characteristics of Life

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Protein-Protein Interfaces

Protein Folding

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Covalently Linked Protein Regulators

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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structural-organization-of-the-human-body-an-overview

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Overview of Human Digestion

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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

What is Homeostasis?

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Negative and Positive Feedback

Homeostatic Imbalance

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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

Modular Protein Complexes in Cells

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