Gi (protein)
The proteins Gi are one of the principal families of the Protéines G associated with a receiver. It acts inter alia receiver muscarinic with acetylcholine, located at the level of the cardiac muscles.
Ces receiving consists of 3 sub-units respectively called α, β, γ. But only first is able to fix a molecule of GDP (Guanosine di Phosphate) or GTP (guanosine triphosphate).
Operation of the receiver to the Acetylcholine
The fixing of the Hormone involves a modification of the structure D of the receiver which stimulates the separation of GDP of Gα, which in its turn is detached from the two other sub-units.
Étant given the prevalence of the GTP on the GDP in the Cytosol, Gα binds to this one, involving the inactivation of a Adénylate cyclase.
The latter catalyzing the reaction ATP --> AMPc, the concentration in AMPC falls in the cell and by there too the activity of the PKA (Protein dependant kinase AMPC). Like PKA phosphoryl plus the ionic channel with related calcium, which prevents the re-entry of Ca++ and decreases the muscular contraction.
Moreover, the sub-units β and γ stimulate the channel with efferent potassium, which creates a cumulative effect on the reduction of the muscular contraction.
Related articles
- See Gq (protein)
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