CAAXGs

CAAXGs refers to a class of small GTPases that are post-translationally modified by prenylation. These proteins are characterized by a C-terminal CaaX motif, where C represents a cysteine residue, a is an aliphatic amino acid, and X is any amino acid. This motif is crucial for their function, as it is recognized by prenyltransferases, enzymes that attach a hydrophobic isoprenoid lipid (geranylgeranyl or farnesyl) to the cysteine residue. This lipid modification is essential for anchoring the GTPases to cellular membranes, facilitating their interactions with downstream effectors and their participation in various signaling pathways.

The CAAX motif is highly conserved across different species, highlighting its fundamental role in GTPase biology. Following prenylation, the CAAX motif is often further processed by specific proteases, leading to the removal of the last three amino acids and sometimes the addition of a methyl group to the newly exposed C-terminal residue. These subsequent modifications can fine-tune the localization and activity of the CAAXG proteins. Examples of CAAXG proteins include Ras, Rho, and Rab families, which are involved in a wide range of cellular processes such as cell growth, differentiation, migration, and intracellular trafficking. Dysregulation of CAAXG protein prenylation has been implicated in various diseases, including cancer and developmental disorders, making them important targets for therapeutic intervention.