Heterotrimeric G protein

Heterotrimeric G proteins are composed of three subunits ( α, β and γ ) existing GTP binding proteins (G- proteins). They are of great importance for the transmission of signals outside the cell into the cell ( signal transduction) and are responsible for physiological (eg, seeing, smelling, blood pressure regulation, etc.) and pathophysiological effects (eg hypertension, heart failure, etc.).

After activation of a G protein -coupled receptor they decay on the one hand to an activated α - subunit and the other in a βγ subunit to exchange GDP for GTP.

Function

Activation of heterotrimeric G proteins

Heterotrimeric G- proteins are allosterically regulated by G- protein - coupled receptors proteins. They can be cyclically activated by these receptors:

Activation of downstream signaling pathways

Activated G proteins are to affect downstream signal transduction pathways in the situation. The α - subunits can for example activate adenylyl cyclase or inhibit change and the concentration of the second messenger cyclic adenosine monophosphate ( cAMP). Furthermore, they can activate phospholipases and protein kinases or modulate ion channels. The βγ subunit may be in the regulation of second messengers of meaning; some effectors, such as certain ion channels that are directly regulated by βγ subunits. About the change in second messenger concentration, a measurable effect is triggered directly or indirectly.

Classification

For signal transduction, in particular, the α - subunit of significance are known from the over 20 isoforms. Based on their properties, these isoforms are essentially in 4 families combined ( αs, ? I, αq and α12/13 ) after which the G proteins are named according to (Gs, Gi, Gq and G12/13 ).