Monomeric GTP binding proteins, also known as small GTPases, are a group of proteins that play a crucial role in various cellular processes, including signal transduction, intracellular transport, cell division, and cytoskeletal rearrangement. These proteins are characterized by their ability to bind and hydrolyze GTP (guanosine triphosphate), a nucleotide molecule that serves as a cellular energy source.
Monomeric GTP binding proteins function as molecular switches, cycling between an active GTP-bound state and an inactive GDP-bound state. In the active state, the protein interacts with downstream effector molecules, initiating signaling cascades and directing cellular processes. Upon hydrolysis of GTP to GDP, the protein is inactivated and dissociates from its effectors, thereby terminating the signal.
The activation and inactivation of monomeric GTP binding proteins are tightly controlled by regulatory proteins, such as guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). GEFs promote the exchange of GDP for GTP, thereby activating the protein, while GAPs enhance the hydrolysis of GTP to GDP, leading to protein inactivation.
Monomeric GTP binding proteins belong to a larger superfamily known as the Ras superfamily, which encompasses several families, including Ras, Rho, Rab, Ran, and Arf proteins. Each family has distinct functions and localizations within the cell, but they all share the common characteristic of binding and hydrolyzing GTP. The dysregulation of monomeric GTP binding proteins has been implicated in various diseases, including cancer, neurodegenerative disorders, and immune system dysfunction.
