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

- [Instructor] Fosforillazione,

l'aggiunta di un gruppo fosfato,

è una modifica importante per le cellule

per regolare la funzione delle proteine.

Quando un gruppo fosfato è
rimosso durante l'idrolisi ATP,

enzimi chiamati protein-chinasi

possono catalizzare il legame
covalente di questo gruppo

a certe catene laterali di
amminoacidi in una proteina.

Di conseguenza, la proteina
cambia forma o consente

ad altre proteine di legare
le regioni fosforilate.

Questi cambiamenti possono
modificare la funzione

della proteina e potrebbe addirittura

attivarlo o disattivarlo completamente.

Il gruppo fosfato può essere rimosso

dall'azione delle proteine fosfatasi,

enzimi che catalizzano la
defosforillazione delle proteine,

essenzialmente invertendo la reazione.

Regolando la fosforillazione
in questo modo,

l'attività di alcune proteine
può essere reversibilmente

accesa, spenta o modificata
secondo necessità nella cella.

Kyriakis, John M. "All'inizio, c'era la fosforilazione delle proteine." The Journal of Biological Chemistry 289, n. 14 (4 aprile 2014): 9460–62. [<a href="https://doi.org/10.1074/jbc.R114.557926" target="__blank">Sorgente</a>]
Ardito, Fatima, Michele Giuliani, Donatella Perrone, Giuseppe Troiano e Lorenzo Lo Muzio. "Il ruolo cruciale della fosforilazione delle proteine nella segnalazione cellulare e il suo uso come terapia mirata (revisione)." International Journal of Molecular Medicine 40, n. 2 (agosto 2017): 271–80. [<a href="https://doi.org/10.3892/ijmm.2017.3036" target="__blank">Sorgente</a>]

fosforilazione

L'aggiunta o la rimozione di gruppi di fosfati dalle proteine è la modifica chimica più comune che regola i processi cellulari. Queste modifiche possono influenzare la struttura, l'attività, la stabilità e la localizzazione delle proteine all'interno delle cellule, nonché le loro interazioni con altre proteine. 

Durante la fosforilalazione, le chinasi proteiche trasferiscono il gruppo terminale di fosfati dell'ATP a specifiche catene laterali di amminoacidi di proteine del substrato. Serina, treonina, e tirosina sono gli aminoacidi più comunemente fosforilati. Di conseguenza, le chinasi proteiche sono classificate come chinasi serine/treonine, chinasi tirosine o chinasi a doppia azione se possono fosforifilare tutti e tre gli aminoacidi. Al contrario, le fosfatasi proteiche catalizzano la rimozione del gruppo fosfato (defosforilazione), ripristinando le proprietà originali della proteina.

In condizioni fisiologiche, il fosforilazione e la defosforilazione sono strettamente regolate per prevenire cambiamenti prolungati nella struttura e nella funzione delle proteine. L'interruzione di questo equilibrio può causare malattie, tra cui il cancro e vari disturbi neurodegenerativi. Ad esempio, una proteina chiamata tau è iperfosforilata nella malattia di Alzheimer (AD). Fisiologicamente, tau regola la forma, struttura, e lo sviluppo dei neuroni. La proteina tau contiene oltre 80 residui di serina, treonina e tirosina, di cui solo una frazione è di solito fosforilata. Nel cervello dei pazienti con AD, il tau è anormalmente ed eccessivamente fosforilato. Questo altera la solubilità della proteina, formando aggregati insolubili tossici che portano alla morte neuronale.

Fosforilazione

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications ...

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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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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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