Control and Alteration of Protein Traffic in the Cell
Normal eukaryotic cell functions rely on cellular systems of protein trafficking control that ensure correct targeting and assembly of specific sets of proteins for membrane-bounded compartments or organelles. The known principles of protein traffic are that destination signals are encoded in the transported proteins themselves and that they are decoded by receptors in the target membranes, for example .
Mitochondria are two-membrane-bounded organelles consisting of 1000–2000 different proteins, more than 99% of which are synthesized in the cytosol as precursor proteins and subsequently imported into mitochondria. Mitochondrial protein import and sorting to one of the four subcompartments, the outer membrane, intermembrane space, inner membrane, and matrix, are mediated by proteinaceous machineries called translocators in the outer and inner mitochondrial membranes [2–5] (Fig. 1). The translocators cooperate with each other to achieve precise as well as efficient protein delivery to their intramitochondrial destinations. A translocator is a protein complex that performs multiple functions. It functions as a receptor for recognition of the targeting as well as sorting signals, and it provides a protein-conducting channel through which precursor proteins go across the membrane in an unfolded state. It also offers a driving force to achieve a vectorial movement of the translocating polypeptide chain.
KeywordsSignal Recognition Particle Nuclear Magnetic Resonance Structure Hydrophobic Groove Outer Membrane Receptor Mitochondrial Target Signal
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