CAAXpää

CAAXpää is a term used in bioinformatics and molecular biology to describe a specific post-translational modification site found in certain proteins. The "CAAX" part refers to a consensus sequence of amino acids where C represents cysteine, A represents an aliphatic amino acid (such as alanine, valine, leucine, or isoleucine), and X represents any amino acid. The "pää" is a Finnish word meaning "head," and in this context, it signifies the N-terminus of a protein or a specific region within it.

This CAAX motif is crucial for prenylation, a process where a lipid molecule, typically farnesyl pyrophosphate or geranylgeranyl pyrophosphate, is attached to the cysteine residue. This lipid modification often occurs at the C-terminus of the protein, although the term CAAXpää can sometimes refer to the motif itself rather than its precise location. Prenylation plays a significant role in protein trafficking, membrane association, and signal transduction. Proteins containing the CAAX motif and undergoing prenylation include Ras GTPases, lamins, and Rab GTPases. The specific aliphatic amino acid at the A position and the terminal amino acid at the X position can influence the type of prenyltransferase that recognizes the motif and the subsequent biological function of the modified protein. Understanding CAAXpää motifs is vital for comprehending protein localization and cellular signaling pathways.