Practice Questions

TLS Online TPP Program

#Question id: 13161

Which of the following mechanism depends on the activation of heterotrimeric G proteins?

#Unit 4. Cell Communication and Cell Signaling

During actin filament formation, the inactive formin is activated when its Rho-binding domain (RBD) binds to membrane-bound active Rho-GTP, resulting in exposure of the formin’s FH2 domain, which can then nucleate the assembly of a new actin filament.
Rod cells sense light with the aid of a light-sensitive rhodopsin which is coupled to transducin. On absorption of a photon, the retinal moiety of rhodopsin is immediately converted from the cis isomeric form to the all-trans isomeric form, causing a conformational change that allows rhodopsin to bind the α subunit of transducin.
Ras proteins are “switch” proteins and not directly linked to cell-surface receptors. Ras activation is accelerated by a guanine nucleotide exchange factor (GEF), which binds to the Ras∙GDP complex, causing dissociation of the bound GDP.
During the regulation of microfilament organization, Cdc42 act as molecular switches, inactive in the GDP-bound state and active in the GTP-bound state.