BIOL 2021 Chapter 12.5: transport of proteins into mitocondria
Document Summary
Compartments: inner and outer membrane, intermembrane space (continuous with cristae, matrix. Transport requires: signal sequence (n-terminal or internal, protein translocators in the membranes, energy source. Protein translocator: mediates protein movement across mitochondrial membranes. Tom complex (translocator of the outer membrane): receptors that recognize a protein"s signal sequence. Tim complex (translocators of inner membrane): don"t have to know the difference between them. Both complexes have receptor components and channel components. Sam (sorting and assembly machinery): outer membrane: insert beta-barrel proteins, helps proteins fold properly, don"t have to know mechanism. Oxa (cytosome oxidase activity): inner membrane: don"t have to know mechanism. Protein is made in the cytosol and binds to chaperone proteins called hsp70 so that it stays unfolded. Tom recognizes the signal sequence and transports it to the intermembrane space and binds to tim where it crosses the inner membrane. Hsp70 helps pull the protein through the pore. Signal sequence is cleaved off with signal peptidase.