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

El trifosfato de guanosina, GTP, un pariente cercano del ATP, es una pequeña molécula importante para la regulación de la función de las proteínas. 
Las proteínas G son proteínas reguladas por la unión a GTP. Estas proteínas tienen actividad GTPasa intrínseca, es decir, cuando se une GTP, pueden catalizar su hidrólisis a difosfato de guanosina, GDP. 
Las proteínas G se dividen en dos categorías, pequeñas y grandes. Las proteínas G pequeñas, o monoméricas, son una sola subunidad de proteína que es activada por varias vías de señalización intracelular.
Por el contrario, las proteínas G grandes, o heterotriméricas, contienen tres subunidades y son activadas por receptores acoplados a proteínas G unidos a la membrana. 
Las GTPasas actúan como un interruptor molecular, donde el estado ligado a GDP generalmente está inactivo mientras que el estado unido a GTP está activo. La unión de GTP seguida de la hidrólisis de GTP a GDP forma parte del ciclo GDP/GTP.
El ciclo comienza cuando un factor de intercambio de guanina, GEF, induce un cambio conformacional en la proteína G que provoca la liberación de GDP. 
GTP se une rápidamente al sitio de unión de nucleótidos ahora vacío, ya que GTP es abundante en el citoplasma. La proteína G ahora pasa a su estado activo con GTP unido. 
Las proteínas G tienen actividad GTPasa intrínseca para hidrolizar la molécula unida; sin embargo, la descomposición de GTP por la enzima es un proceso lento sin señales celulares adicionales.
Por lo tanto, cuando llega el momento de desconectar la proteína G, una proteína activadora de GTPasa, o GAP, se unirá y mejorará la actividad de la GTPasa de la proteína. El GTP se descompone en GDP y fosfato inorgánico y la proteína G vuelve a su estado inactivo completando el ciclo.

<ol>
	<li>Mishra, A. K., & Lambright, D. G. (2016). Revisión invitada: GTPasas pequeñas y sus GAPs. Biopolímeros, 105(8), 431–448.</li>
	<li>Toma-Fukai, S., & Shimizu, T. (2019). Perspectivas estructurales sobre el mecanismo de regulación de las pequeñas GTPasas por parte de los FMAM. Moléculas (Basilea, Suiza), 24(18), 3308.</li>
</ol>

gtpasas y su regulación

Las proteínas de unión a nucleótidos de guanina (proteínas G), también conocidas como GTPasas, son una superfamilia de proteínas que regulan muchos procesos celulares, como la señalización celular, el transporte vesicular y la regulación de la forma y motilidad celular. La mutación o disfunción de estas proteínas puede provocar enfermedades. Hay alrededor de 40.000 proteínas G conocidas que, en términos generales, pueden clasificarse en dos grupos: proteínas G pequeñas que constan de un solo dominio y proteínas G grandes de dominios múltiples.

Las proteínas G grandes, también conocidas como proteínas G heterotriméricas, constan de tres subunidades: α, β y γ. La subunidad α tiene un dominio conservado que interactúa con receptores acoplados a proteína G para mediar la señalización transmembrana.

Las proteínas G pequeñas son una subunidad única y envían señales a toda la célula a través de una variedad de vías. Se dividen en cinco subfamilias según su secuencia y función: Ras, Rho, Rab, Ran y Arf. Las mutaciones en la subfamilia Ras conducen a la formación de tumores cancerosos en los pulmones, el colon y el páncreas. La subfamilia Rho regula la reorganización de la actina y la dinámica del citoesqueleto de los microtúbulos. La subfamilia Rab, la familia pequeña de proteínas G más grande, regula el transporte de vesículas y el tráfico de membranas en vías secretoras y endocíticas. La subfamilia Ran regula el transporte nucleocitoplasmático de ARN y proteínas a través del ensamblaje y función del poro nuclear y del huso mitótico. La subfamilia Arf participa en el transporte de vesículas y el tráfico de membranas.

Las proteínas G están reguladas por la unión de GTP/GDP y tienen actividad GTPasa intrínseca, lo que significa que pueden hidrolizar GTP a GDP. Cuando se une GTP, la proteína G está en estado "ENCENDIDO", es decir, la proteína promoverá cascadas de señalización en la célula. Cuando el PIB está limitado, está en el estado "APAGADO", lo que provoca que la señalización se detenga. La regulación de la activación de la proteína G está regulada además por los factores de intercambio de nucleótidos de guanina (GEF), que ayudan en la disociación del GDP, y las proteínas activadoras de la GTPasa (GAP) que estimulan la hidrólisis del GTP. Además, los inhibidores de la disociación de guanina (GDI) pueden unirse a pequeñas GTPasas y regular su ubicación en la membrana o el citoplasma.

GTPasas y su regulación

Las proteínas de unión a nucleótidos de guanina (proteínas G), también conocidas como GTPasas, son una superfamilia de proteínas que regulan muchos procesos celulares, como ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Protein Function

Función proteica

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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

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protein kinases and phosphatases

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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

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protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

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structural protein function

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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

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HS-LS1-3

GTPase Molecular Switches and Control

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