Heterotrimeric guanosine triphosphate binding protein, also known as G-protein, refers to a class of proteins that play a critical role in cellular signaling and communication processes in organisms. These proteins are involved in transmitting extracellular signals from various receptors to its respective cellular targets.
Heterotrimeric G-proteins are composed of three distinct subunits: α, β, and γ. The α subunit anchors the protein to the cell membrane and possesses the ability to bind and hydrolyze guanosine triphosphate (GTP). The β and γ subunits, on the other hand, remain together and are also associated with the cell membrane.
The activation of heterotrimeric G-proteins begins when a signaling molecule or ligand binds to a specific receptor on the cell surface. This binding triggers a conformational change in the receptor, allowing it to interact with the G-protein complex. Upon binding, the G-protein becomes activated and exchanges bound GDP (guanosine diphosphate) with GTP on the α subunit.
Once GTP is bound, the α subunit dissociates from the βγ subunits, leading to the activation of multiple downstream signaling pathways. The activated α subunit can directly interact with various effector molecules or enzymes, triggering a cascade of intracellular events. The βγ subunits can also independently interact with their own target proteins, further amplifying the signaling pathways.
The activity of heterotrimeric G-proteins is tightly regulated by GTPase activity, which hydrolyzes the bound GTP to GDP. This hydrolysis process switches off the G-protein signaling and allows the α subunit to reassociate with the βγ subunits, forming an inactive state.
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