Small G proteins, also known as small GTPases, are a class of proteins that play crucial roles in various cellular processes, acting as molecular switches that regulate signal transduction pathways. These proteins are approximately 20-30 kilodalton in size and are characterized by their ability to bind with guanosine nucleotides, particularly guanosine triphosphate (GTP), which allows them to cycle between active (GTP-bound) and inactive (GDP-bound) states.
Small G proteins are found in all eukaryotic cells and are involved in diverse physiological processes, such as cell growth and division, cytoskeletal reorganization, membrane trafficking, and the regulation of gene expression. Their activity is tightly regulated by guanine nucleotide exchange factors (GEFs), which facilitate the exchange of GDP for GTP, and GTPase-activating proteins (GAPs), which promote the hydrolysis of GTP back to GDP, thus turning off their signaling activity.
The activation of small G proteins is often triggered by extracellular signals, such as growth factors or cytokines, which induce conformational changes that allow GTP binding. When activated, small G proteins interact with downstream effector proteins to initiate a cascade of intracellular signaling events, ultimately leading to specific cellular responses.
Due to their pivotal roles in cellular processes, malfunction or dysregulation of small G proteins is implicated in various diseases, including cancer, neurological disorders, and immunological disorders. As a result, small G proteins have become attractive therapeutic targets, and efforts are being made to develop drugs that modulate their activity for the treatment of these diseases.
