Receptors and signal transduction

17 important questions on Receptors and signal transduction

Where does a G-proitein constist of?

A G-protein consists of an alfa-subunit bound to GDP and a beta-gamma-dimer-subunit.

What happens after bidning the G-protein?

The GDP in the alfa-subunit is exchanged for GTP. Then the G-protein fragments in the alfa-subunit and the beta-gamma-subunit.

What leads to signal amplification in G-proteins?

As long as the messenger is bound the subunits are separated leading to signal amplification.
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What does the alfa-s-subunit?

The alfa-s-subunit binds adenylate cyclase and activates it such that it catalyzes the formation of cAMP from ATP. This is for as long as the chemical messenger is bound and amplifies the signal even more.

What happens when the signal stops?

The alfa-subunit hydrolyze GTP to GDP. Now the adenylate cyclase is left and the alfa-subunit reforms with the beta-gamma dimer.

How is the overal activity of adenylate cyclase determined?

The activity of adenylate cyclase is regulated by Gi and Gs proteins.

What is the function of the beta-gamma-dimer?

The beta-gamma-dimer has a moderate role in the activity of adenylate cyclase and other enzymes when they are present in relatively high concentrations.

What do the serine-threonine kinase receptros?

The serine-threonine kinases phosphorylate the alcohol groups of serine and threonine. The conformational change results in affecting the activity of the substrate enzyme.

Are kinases involved in desensitization of receptors?

Yes.

What does the alfa-q-subunit of the Gq-protein?

Alfa-q-subunit affects the activity of phospholipase C.

What does phospholipase C?

Phospholipase C catalyzes the hydrolysis of PIP2 to form the secondary messenger IP3 and DG.

How is PIP2 synthesized?

PIP is synthesized by the reformation of IP3 and DG is a series of steps.

What do lithium salts?

Lithium salts are believed to interfere with the reformation of PIP2.

What is important to the phosphorylation of tyrosine residues?

Activated kinases receptor acts as binding sites for various signaling proteins and activates enzymes in turn.

What are small G-proteins?

Small G-proteins are similar to G-proteins binding GDP in resting state and GTP in the activated state.

How are small G-proteins activated?

Guanine nucleotide exchange factors activate small G-proteins.

Can some kinases with their intracellular active site catalyze the formation of cyclic GMP form GTP?

Yes.

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