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

Kompleksy białkowe składają się z wielu niekowalencyjnie połączonych białek, z których każdy składnik pełni inną funkcję w stosunku do kompleksu. 
Jedno lub więcej z tych pojedynczych białek można zastąpić ściśle spokrewnionymi wariantami, aby stworzyć alternatywny kompleks, który jest funkcjonalnie odrębny.
W miarę ewolucji organizmu gen korzystnego białka może duplikować się w genomie. Ta zduplikowana kopia może swobodnie ulegać mutacjom bez wpływu na funkcję oryginalnego białka. 
Mutacje te generują rodziny pokrewnych białek. Jest to jeden ze sposobów, w jaki komórka może wytworzyć kompleks białkowy zawierający wymienne części. 
Ligaza ubikwityny SCF jest białkiem multimerycznym zbudowanym z pięciu podjednostek. Jego funkcją jest przyłączanie cząsteczek ubikwityny do białek docelowych, oznaczając je do degradacji przez enzymy proteolityczne. 
Jedna z podjednostek białka, F-box, która jest odpowiedzialna za wiązanie się z białkiem docelowym, ma kilka wariantów, które są wymienne. Zmiana w tej podjednostce umożliwia kompleksowi oznaczanie różnych białek do degradacji. 
Saccharomyces cerevisiae, powszechnie znane jako drożdże piekarskie, mają 11 wariantów podjednostek F-box, umożliwiających ligazie oznaczanie białek biorących udział w różnych procesach komórkowych.
Na przykład białko F-box cdc4 jest ukierunkowane na regulatory cyklu komórkowego, takie jak Sic1 i Far1, które hamują enzymy promujące cykl komórkowy. Ich degradacja umożliwia kontynuowanie cyklu komórkowego. 
Zmienność F-box w różnych organizmach generuje setki odrębnych kompleksów o podobnych funkcjach, ale odrębnych celach.

<ol>
	<li>Alberts et al., wydanie 6; strony 159-160</li>
	<li>Kipreos, E. T., & Pagano, M. (2000). Rodzina białek F-box. Biologia genomu, 1(5), REVIEWS3002. doi:10.1186/gb-2000-1-5-reviews300</li>
</ol>

kompleksy białkowe z wymiennymi częściami

Grupy białek mogą tworzyć kompleks, w którym każde białko pełni inną rolę w realizacji funkcji całości. Często niektóre białka w kompleksie można zastąpić blisko spokrewnionym wariantem, aby uzyskać kompleks, który zawiera wiele tych samych składników, ale jest funkcjonalnie odrębny. Ligaza ubikwityny SCF jest kompleksem składającym się z pięciu pojedynczych białek. Kompleks ten przyłącza ubikwitynę do innych białek docelowych, aby oznaczyć je do degradacji. Aby pełnić tę funkcję, jedno z białek, F-box, jest odpowiedzialne za wiązanie się z substratem, umożliwiając w ten sposób innemu białku w kompleksie, enzymowi sprzęgającemu ubikwitynę, dostęp do substratu i przyłączenie ubikwityny. Białko F-box ma wiele wymiennych wariantów, dzięki czemu kompleks może rozpoznawać różne substraty. Dodatkowo, różne organizmy mogą mieć różne zestawy wariantów białka F-box. Ludzie mają 38 znanych wariantów, Saccharomyces cerevisiae ma 11, Drosophila ma 22, a C. elegans ma 326. Ta zmienność umożliwia kompleksowi celowanie w duże spektrum białek poprzez zmianę tylko jednego z jego składników. Te wymienne warianty są często wynikiem duplikacji genów. Podczas ewolucji molekularnej gen dla korzystnego białka może czasami powielać się podczas replikacji DNA z powodów takich jak rekombinacja ektopowa, poślizg replikacyjny, aneuploidia, poliploidia i retrotranspozycja. Ta zduplikowana kopia genu może dalej ulegać mutacjom podczas przenoszenia z pokolenia na pokolenie, ponieważ mutacja nie wpływa na funkcję oryginalnego genu. Mutacje te skutkują wariantami genu, które są odpowiedzialne za białka, takie jak F-box, które są funkcjonalnie podobne, ale mają różne specyficzności substratowe.

Kompleksy białkowe z wymiennymi częściami

Grupy białek mogą tworzyć kompleks, w którym każde białko w tym kompleksie odgrywa inną rolę w ogólnym wykonywaniu funkcji kompleksu. ...

Education

JoVE Core

Cell Biology

Biologia komórki

Unit 1

Jednostka 1

Protein Function

Funkcja białka

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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 Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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Protein Kinases and Phosphatases

GTPases and their Regulation

Covalently Linked Protein Regulators

Mechanical Protein Function

Structural Protein Function

Protein Networks

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HS-LS1-2

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HS-LS1-3

Modular Protein Complexes in Cells

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