GTPase

GTPases (singular GTPase) are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases.

Functions

GTPases play an important role in:

Signal transduction at the intracellular domain of transmembrane receptors, including recognition of taste, smell and light.

Transport of vesicles within the cell. (GTPases control assembly of vesicle coats.)

The hydrolysis of the γ phosphate of GTP into guanosine diphosphate (GDP) and P_i, inorganic phosphate, occurs by the S_N2 mechanism (see nucleophilic substitution) via a pentavalent intermediate state and is dependent on the magnesium ion Mg²⁺.

In most GTPases, the specificity for the base guanine is imparted by the base-recognition motif, which has the consensus sequence [N/T]KXD.

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