MACROMOLECULAR MOVEMENT INTO MITOCHONDRIA

Publisher Summary This chapter discusses macromolecular movement into mitochondria. Genetic information in plants is localized in three subcellular compartments, the nucleus, mitochondria, and chloroplasts, hence there is a need for coordination of expression between the nuclear and the organellar genomes. The majority of plant organellar macromolecules are nuclear encoded. The biogenesis of all cellular organelles requires specific intracellular protein trafficking and import systems because their nuclear-encoded proteins are synthesized in the cytosol. Many of the nuclear-encoded proteins are synthesized as precursor proteins containing N-terminal extensions called “signal peptides,” “presequences,” or “transit peptides,” which function as organellar sorting and targeting signals. Most of the proteins destined to mitochondria, chloroplasts, and endoplasmic reticulum (ER) contain N-terminal signals, which are proteolytically cleaved off after the completed import. Noncleavable C-terminal and N-terminal targeting signals for transport into peroxisomes and internal signals for transport to the nucleus have also been characterized.