Fehérjetargetálás

Fehérjetargetálás, also known as protein targeting or protein localization, is the process by which cells direct newly synthesized proteins to their correct destinations within the cell or for secretion outside the cell. This intricate mechanism ensures that proteins perform their specific functions in the right cellular compartments. The process often begins in the cytoplasm on ribosomes, where the nascent polypeptide chain emerges. Specific signal sequences, typically short amino acid stretches, are recognized as targeting signals. These sequences act like molecular zip codes, dictating where the protein should go.

Several pathways exist for protein targeting. For proteins destined for secretion, insertion into membranes, or delivery to organelles like the endoplasmic reticulum, Golgi apparatus, lysosomes, or peroxisomes, the signal recognition particle (SRP) pathway is crucial. The SRP binds to the signal sequence and the ribosome, halting translation and escorting the complex to the endoplasmic reticulum membrane. There, the protein is translocated into the ER lumen or integrated into the ER membrane. Proteins destined for the nucleus, mitochondria, chloroplasts, or peroxisomes often utilize a post-translational targeting mechanism, where fully synthesized proteins are imported into these organelles. This process involves specific receptor proteins on the organelle membrane that recognize and bind to the targeting signals on the protein. Understanding protein targeting is fundamental to comprehending cellular organization and function, and it has significant implications for understanding and treating diseases arising from protein mislocalization.