Name: phosphorylation and protein control
Uploaded: 2019-03-11T09:21:10.000Z
Duration: 1 min 2 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.4

LS.4.b

Phosphorylation

- Fosforilação, a adição de um grupo fosfato, é uma modificação importante para as células para regular a função da proteína. 
Quando um grupo fosfato é removido durante a hidrólise do ATP, enzimas chamadas de proteína cinases pode catalisar a ligação covalente deste grupo a certas cadeias laterais de aminoácidos em uma proteína. 
Como resultado, a proteína muda de forma ou permite que outras proteínas se liguem às regiões fosforiladas. 
Essas mudanças podem modificar a função de uma proteína e pode até mesmo ativá-lo ou desativá-lo completamente. 
O grupo fosfato pode ser removido pela ação das proteínas fosfatases, enzimas que catalisam a desfosforilação de proteínas, essencialmente invertendo a reação. 
Ao regular a fosforilação desta maneira, a atividade de certas proteínas pode ser reversívelmente ligado, desligado ou modificado conforme necessário na célula.

Kyriakis, John M. "No início, havia fosforilação de proteínas." The Journal of Biological Chemistry 289, nº 14 (4 de abril de 2014): 9460–62. [<a href="https://doi.org/10.1074/jbc.R114.557926" target="__blank">Fonte</a>]
Ardito, Fátima, Michele Giuliani, Donatella Perrone, Giuseppe Troiano e Lorenzo Lo Muzio. "O papel crucial da fosforilação de proteínas na sinalização celular e seu uso como terapia direcionada (revisão)." International Journal of Molecular Medicine 40, nº 2 (agosto de 2017): 271–80. [<a href="https://doi.org/10.3892/ijmm.2017.3036" target="__blank">Fonte</a>]

fosforilação

A adição ou remoção de grupos fosfato de proteínas é a modificação química mais comum que regula processos celulares. Essas modificações podem afetar a estrutura, atividade, estabilidade e localização de proteínas dentro das células, bem como as suas interações com outras proteínas. 
 
 Durante a fosforilação, as quinases proteicas transferem o grupo fosfato terminal do ATP para cadeias laterais específicas de aminoácidos de proteínas substrato. Serina, treonina e tirosina são os aminoácidos mais comumente fosforilados. Assim, as quinases proteicas são classificadas como quinases de serina/treonina, quinases de tirosina ou quinases de ação dupla se puderem fosforilar todos os três aminoácidos. Por outro lado, as fosfatases proteicas catalisam a remoção do grupo fosfato (desfosforilação), restaurando as propriedades originais da proteína.
 
 Em condições fisiológicas, a fosforilação e a desfosforilação são fortemente reguladas para evitar alterações prolongadas na estrutura e função proteicas. A interrupção desse equilíbrio pode causar doenças, incluindo cancro e vários distúrbios neurodegenerativos. Por exemplo, uma proteína chamada tau é hiperfosforilada na doença de Alzheimer (DA). Fisiologicamente, a tau regula a forma, estrutura e desenvolvimento de neurónios. A proteína tau contém mais de 80 resíduos de serina, treonina e tirosina, dos quais apenas uma fração é geralmente fosforilada. No cérebro de pacientes com DA, a tau é anormal e excessivamente fosforilada. Isso altera a solubilidade da proteína, formando agregados tóxicos insolúveis que levam à morte neuronal.

Fosforilação

A adição ou remoção de grupos fosfato das proteínas é a modificação química mais comum que regula os processos celulares. Essas modificações ...

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phosphorylation and protein control

Phosphorylation helps control how proteins work in cells. It is the addition or removal of phosphate groups, and it is the most common chemical change that regulates cellular processes. These changes can alter a protein’s structure, activity, stability, location inside the cell, and interactions with other proteins.

During phosphorylation, protein kinases move the terminal phosphate group from ATP to a specific amino acid side chain on a target protein. The amino acids most often phosphorylated are serine, threonine, and tyrosine. Protein kinases are grouped as serine/threonine kinases, tyrosine kinases, or dual action kinases when they can phosphorylate all three.

Protein phosphatases carry out the reverse step. They remove the phosphate group in a process called dephosphorylation, which restores the protein’s original properties. In healthy cells, phosphorylation and dephosphorylation are carefully balanced so protein shape and function do not stay changed for too long.

When this balance is disrupted, disease can result. Examples include cancer and several neurodegenerative disorders. Tau is one important example. In healthy neurons, tau helps regulate neuron shape, structure, and development. Tau has more than 80 serine, threonine, and tyrosine sites, but only some are normally phosphorylated. In Alzheimer’s disease, tau becomes hyperphosphorylated, or abnormally over-phosphorylated. This makes the protein less soluble and leads to toxic insoluble aggregates that contribute to neuronal death.

Phosphorylation and Protein Control

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Phosphorylation helps control how proteins work in cells. It is the addition or removal of phosphate groups, and it is the most common chemical change that regulates cellular processes. These changes can alter a protein’s structure, activity, stability, location inside the cell, and interactions with other proteins. During phosphorylation, protein kinases move the terminal phosphate group from ATP to a specific amino acid side chain on a target protein. The amino acids most often...

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key terms and concepts

Learn how kinases add phosphate groups, phosphatases remove them, and why balanced phosphorylation matters for cell function and diseases like Alzheimer’s.

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Phosphorylation and Protein Control

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