G Protein Quiz

Imagine a city's traffic system where G proteins are the traffic lights. What happens when these traffic lights (G proteins) are switched to green (active conformation)?

• They are turned off and stop controlling the traffic flow (bind GDP and are inactive).

• They signal the maintenance crew to perform checks (catalyze the hydrolysis of GTP to GDP).

• They change the traffic flow, allowing cars (βγ) to move freely and direct them towards their destination (interact with the effector).

• They prepare for the next cycle of traffic control by resetting (facilitate the exchange of GDP for GTP in the α-subunit).

What is the primary function of small GTPases?

• To directly activate G protein-coupled receptors.

• To act as molecular "switches" in signaling pathways.

• To increase the rate of GTP hydrolysis.

• To facilitate nucleotide exchange in regulatory proteins.

What is the effect of GTP hydrolysis on monomeric G proteins?

• It leads to the activation of the protein.

• It promotes the interaction with GEFs.

• It results in the inactivation of the protein.

• It increases the affinity for the effector.

Which proteins facilitate the exchange of bound GDP for free cytosolic GTP in small GTPases?

• GTPase-activating proteins (GAPs)

• Guanine nucleotide exchange factors (GEFs)

• Effector proteins

• Small GTPases themselves

Which family of small GTPases is specifically mentioned as being identified in over 150 human monomeric forms?

• Rab

• Rho

• Ras

• Ran

What is the primary function of GTPase-Activating Proteins (GAPs)?

• They accelerate GTP hydrolysis.

• They inhibit GTP hydrolysis.

• They facilitate the binding of GTP to small GTPases.

• They prevent the association of small GTPases with membranes.

Which of the following is a consequence of mutations in Ras proteins found in human cancers?

• They become sensitive to GAP stimulation.

• They are unable to bind GTP.

• They are insensitive to GAP stimulation and remain persistently GTP-bound.

• They accelerate GTP hydrolysis.

What do Guanine Nucleotide Dissociation Inhibitors (GDIs) inhibit?

• The activation of small GTPases by GEFs.

• The hydrolysis of GTP by small GTPases.

• The association of small GTPases with membranes.

• The binding of GAPs to small GTPases.

Which family of small GTPases is involved in the regulation of cell proliferation and differentiation?

• Rab family

• Rho family

• Ras family

• Arf family

What is the function of the Rab family of small GTPases?

• Regulation of gene expression

• Membrane trafficking

• Actin cytoskeletal organization

• Hydrolysis of GTP