Guanine Nucleotide-Binding Proteins (G-Proteins)

G-proteins, what do they do

Bind Guanine Nucleotides

• Guanosine diphosphate (GDP)

• Guanosine triphosphate (GTP)

• Negative charge on oxygen

G-proteins are

GTPases that Catalyze Hydrolysis of GTP to GDP

G-proteins Must

Release GDP to Bind Another GTP Molecule

The GTP-bound State

is the Active Conformation

GAPs

GTPase Activating Proteins (GAPs) Increase GTPase Activity

GEFs

Guanine Nucleotide Exchange Factors (GEFS)

Stimulate GDP Release

G-Proteins Act as

Molecular Switches

• G-proteins are either “on” or “off”

• Can be quickly switched between these two states

• Key for temporal and spatial regulation of cellular processes

G-proteins

catalyze GTP hydrolysis

GTP-bound state

is the active conformation

GDP-bound state

is the inactive conformation

GAPs

stimulate GTP hydrolysis/inactive state

GEFs

stimulate GDP release/active state