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

Trifosforan guanozyny, GTP, bliski krewny ATP, jest małą cząsteczką ważną dla regulacji funkcji białek. 
Białka G to białka regulowane przez wiązanie GTP. Białka te mają wewnętrzną aktywność GTPazy, to znaczy, gdy GTP jest związany, mogą katalizować jego hydrolizę do difosforanu guanozyny, GDP. 
Białka G dzielą się na dwie kategorie, małe i duże. Małe lub monomeryczne białka G są pojedynczą podjednostką białkową, która jest aktywowana przez różne wewnątrzkomórkowe szlaki sygnałowe.
W przeciwieństwie do tego, duże lub heterotrimeryczne białka G zawierają trzy podjednostki i są aktywowane przez receptory sprzężone z białkiem G związanym z błoną. 
GTPazy działają jak przełącznik molekularny, w którym stan związany GDP jest zwykle nieaktywny, podczas gdy stan związany GTP jest aktywny. Wiązanie GTP, a następnie hydroliza GTP z GDP jest częścią cyklu PKB/GTP.
Cykl rozpoczyna się, gdy czynnik wymiany guaniny, GEF, indukuje zmianę konformacyjną w białku G, która powoduje uwalnianie GDP. 
GTP szybko wiąże się z pustym już miejscem wiązania nukleotydów, ponieważ GTP występuje obficie w cytoplazmie. Białko G jest teraz przełączane w stan aktywny z wiązaniem GTP. 
Białka G mają wewnętrzną aktywność GTPazy do hydrolizy związanej cząsteczki, jednak rozkład GTP przez enzym jest powolnym procesem bez dodatkowych sygnałów komórkowych.
Dlatego, gdy nadejdzie czas na wyłączenie białka G, białko aktywujące GTPazę lub GAP zwiąże się i zwiększy aktywność GTPazy białka. GTP jest rozkładany na PKB i fosforan nieorganiczny, a białko G powraca do stanu nieaktywnego, kończąc cykl.

<ol>
	<li>Mishra, AK i Lambright, DG (2016). Zaproszona recenzja: Małe GTPazy i ich GAPy. Biopolimery, 105(8), 431–448.</li>
	<li>Toma-Fukai, S. i Shimizu, T. (2019). Strukturalne spostrzeżenia na temat mechanizmu regulacji małych GTPaz przez GEF. Molekuły (Bazylea, Szwajcaria), 24(18), 3308.</li>
</ol>

owspazy i ich regulacja

Białka wiążące nukleotydy guaninowe (białka G), znane również jako GTPazy, to nadrodzina białek regulujących wiele procesów komórkowych, takich jak sygnalizacja komórkowa, transport pęcherzykowy oraz regulacja kształtu i ruchliwości komórek. Mutacja lub dysfunkcja tych białek może prowadzić do choroby. Istnieje około 40 000 znanych białek G, które można ogólnie podzielić na dwie grupy – małe białka G składające się z pojedynczej domeny i duże, wielodomenowe białka G. Duże białka G, znane również jako heterotrimeryczne białka G, składają się z trzech podjednostek — α, β i γ. Podjednostka α ma konserwatywną domenę, która oddziałuje z receptorami sprzężonymi z białkiem G, pośrednicząc w sygnalizacji przezbłonowej. Małe białka G stanowią pojedynczą podjednostkę i przekazują sygnał w całej komórce różnymi szlakami. Dzielą się na pięć podrodzin w oparciu o sekwencję i funkcję – Ras, Rho, Rab, Ran i Arf. Mutacje w podrodzinie Ras prowadzą do powstawania guzów nowotworowych w płucach, okrężnicy i trzustce. Podrodzina Rho reguluje reorganizację aktyny i dynamikę cytoszkieletu mikrotubul. Podrodzina Rab, największa rodzina małych białek G, reguluje transport pęcherzyków i przemieszczanie się błon w szlakach wydzielniczych i endocytarnych. Podrodzina Ran reguluje nukleocytoplazmatyczny transport RNA i białek przez pory jądrowe oraz montaż i funkcję wrzeciona mitotycznego. Podrodzina Arf bierze udział w transporcie pęcherzyków i transporcie błonowym. Białka G są regulowane przez wiązanie GTP/GDP i mają wewnętrzną aktywność GTPazy, co oznacza, że mogą hydrolizować GTP do GDP. Kiedy GTP jest związany, białko G znajduje się w stanie „ON”, co oznacza, że białko będzie promować kaskady sygnalizacyjne w komórce. Kiedy GDP jest związany, znajduje się w stanie „OFF”, co powoduje zatrzymanie sygnalizacji. Regulacja aktywacji białka G jest dodatkowo regulowana przez czynniki wymiany nukleotydów guaninowych (GEF), które pomagają w dysocjacji GDP, oraz białka aktywujące GTPazę (GAP), które stymulują hydrolizę GTP. Ponadto inhibitory dysocjacji guaniny (GDI) mogą wiązać się z małymi GTPazami i regulować ich lokalizację w błonie lub cytoplazmie.

OWSPazy i ich regulacja

Białka wiążące nukleotydy guaniny (białka G), znane również jako GTPazy, to nadrodzina białek, które regulują wiele procesów komórkowych, takich jak ...

Education

JoVE Core

Cell Biology

Biologia komórki

Unit 1

Jednostka 1

Protein Function

Funkcja białka

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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

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protein-protein interfaces

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conserved binding sites

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cooperative allosteric transitions

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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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mechanical protein function

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structural protein function

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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

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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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