基因 Chapter 10 Protein Localization.pdf

Protein Localization CHAPTER OUTLINE IDI Introduction IDD The Hsp70 Family Is Ubiquitous lIB Passage Across a Membrane Requires a Special Apparatus • Members of the Hsp70 family are found in the cytosol, in the ER, and in mitochondria and chloroplasts. • Proteins pass across membranes through specialized protein structures embedded in the membrane. • Hsp70 is a chaperone that functions on target proteins in conjunction with DnaJ and GrpE. • Substrate proteins interact directly with the transport appa­ ratus of the ER, mitochondria, or chloroplasts, but require 1mB Signal Sequences Initiate Translocation carrier proteins to interact with peroxisomes. • Proteins associate with the ER system only cotranslationally. • A much larger and complex apparatus is required for trans­ • The signal sequence of the substrate protein is responsible port into the nucleus. for membrane association. Protein Translocation May Be Posttranslational lID The Signal Sequence Interacts with the SRP or Cotranslational • The signal sequence binds to the SRP (signal recognition • Proteins that are imported into cytoplasmic organelles are