Name: gtpase molecular switches and control
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 2 min 14 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

GTPases and their Regulation

O trifosfato de guanosina, GTP, um parente próximo de ATP, é uma molécula pequena importante para a regulação da função da proteína. As proteínas G são reguladas por ligação de GTP. Estas proteínas têm atividade intrínseca de GTPase.Isto é, quando o GTP está ligado, podem catalisar sua hidrólise ao difosfato de guanosina, GDP. As proteínas G são divididas em duas categorias, pequenas e grandes. As proteínas G pequenas, ou monoméricas, são uma única subunidade proteica que é ativada por várias vias de sinalização intracelular.Em contraste, as proteínas G grandes, ou oligoméricas, contêm três subunidades, e são ativadas por recetores acoplados à proteína G.As GTPases agem como um interruptor molecular, onde o estado limite da GDP geralmente está inativo, enquanto o estado limite da GTP está ativo. A ligação do GTP é seguida pela hidrólise do GTP a GDP, sendo parte do ciclo GTP GDP. O ciclo começa quando um fator de troca guanina, ou um GEF, induz uma mudança conformacional na proteína G que causa a liberação do GDP.O GTP liga-se rapidamente ao sítio da ligação nucleotídica agora vazio, como o GTP é abundante no citoplasma. A proteína G está agora comutada em seu estado ativo, com ligação de GTP. As proteínas G têm atividade intrínseca de GTPase para hidrolisar a molécula ligada.No entanto, a quebra do GTP pela enzima é um processo lento, sem sinais de células adicionais. Portanto, quando é o momento da proteína G ser desligada, uma proteína ativadora de GTPase, ou LACUNA, vai ligar e aumentar a atividade de GTPase da proteína. O GTP é dividido em GDP e fosfato inorgânico, e a proteína G retorna ao seu estado inativo, completando o ciclo.

<ol>
	<li>Mishra, A. K., & Lambright, D. G. (2016). Revisão convidada: Pequenos GTPases e seus GAPs. Biopolímeros, 105(8), 431–448.</li>
	<li>Toma-Fukai, S., & Shimizu, T. (2019). Insights estruturais sobre o mecanismo de regulação de pequenas GTPases por GEFs. Moléculas (Basileia, Suíça), 24(18), 3308.</li>
</ol>

gtpases e sua regulação

As proteínas de ligação ao nucleotídeo guanina (proteínas G), também conhecidas como GTPases, são uma superfamília de proteínas que regulam muitos processos celulares, como sinalização celular, transporte vesicular e regulação da forma e motilidade celular. A mutação ou disfunção dessas proteínas pode levar à doença. Existem cerca de 40.000 proteínas G conhecidas que podem ser amplamente classificadas em dois grupos: proteínas G pequenas que consistem em um único domínio e proteínas G grandes com vários domínios. As proteínas G grandes, também conhecidas como proteínas G heterotriméricas, consistem em três subunidades: α, β e γ. A subunidade α possui um domínio conservado que interage com receptores acoplados à proteína G para mediar a sinalização transmembrana. As pequenas proteínas G são uma subunidade única e sinalizam por toda a célula em uma variedade de vias. Elas são divididas em cinco subfamílias com base na sequência e função: Ras, Rho, Rab, Ran e Arf. Mutações na subfamília Ras levam à formação de tumores cancerígenos nos pulmões, cólon e pâncreas. A subfamília Rho regula a reorganização da actina e a dinâmica do citoesqueleto dos microtúbulos. A subfamília Rab, a maior família de pequenas proteínas G, regula o transporte de vesículas e o tráfego de membrana nas vias secretoras e endocíticas. A subfamília Ran regula o transporte nucleocitoplasmático de RNA e proteínas através do poro nuclear e da montagem e função do fuso mitótico. A subfamília Arf está envolvida no transporte de vesículas e no tráfego de membranas. As proteínas G são reguladas pela ligação GTP/GDP e possuem atividade intrínseca de GTPase, o que significa que podem hidrolisar GTP em GDP. Quando o GTP está ligado, a proteína G fica no estado “ligado”, ou seja, a proteína promoverá cascatas de sinalização na célula. Quando o GDP está vinculado, ela fica no estado “desligado”, fazendo com que a sinalização pare. A ativação da proteína G é regulada ainda mais por fatores de troca de nucleotídeos de guanina (GEFs), que auxiliam na dissociação do GDP, e por proteínas ativadoras de GTPase (GAPs), que estimulam a hidrólise do GTP. Além disso, os inibidores da dissociação da guanina (GDIs) podem ligar-se a pequenas GTPases e regular a sua localização na membrana ou no citoplasma.

GTPases e sua Regulação

As proteínas ligadoras de nucleotídeos de guanina (proteínas G), também conhecidas como GTPases, são uma superfamília de proteínas que regulam muitos processos celulares, como ...

Education

JoVE Core

Cell Biology

Biologia Celular

Unit 1

Unidade 1

Protein Function

Função Proteica

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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 by other proteins as well. Some proteins help GTPases exchange GDP for GTP, while others speed up GTP breakdown. These regulators make sure GTPases respond at the right time and in the right place.

GTPase Molecular Switches and Control

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

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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

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

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 how GTPases act as molecular switches and how GTP and GDP binding, plus regulator proteins, control when they are active or inactive.

GTPase Molecular Switches and Control | JoVE K12

cell biology

JoVE Core - Biologia Celular ilustra processos celulares complexos em vídeos de animação fáceis de entender e, ao mesmo tempo, abrangentes. Esta coleção foca nos componentes e funções essenciais das células, incluindo organelas e membranas, transporte celular e energia celular. É complementado por vídeos de Cientistas em ação que demonstram a aplicação da biologia celular em experimentos de pesquisa do mundo real.

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HS-LS1-2

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HS-LS1-3

GTPase Molecular Switches and Control

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