LIFE 210 Lecture Notes - Oligosaccharide, Cytosol, Glycosylation
Document Summary
The er is organized into a net of tubules and flattened sacs. Constitutes about half of the total membranes in an animal cell. It is the site of production of transmembrane proteins and lipids for most organelles. Soluble proteins for secretion or lumen of er, golgi apparatus, lysosomes. Ribosomes bind to the er membrane during co-translational translation. Signal sequences were first discovered in proteins imported into the rough er (1970"s) The er signal sequence varies greatly but each has 8 or more hydrophobic amino acids at its center. The signal recognition particle (srp) and its receptor. Srp binds the signal sequence as it emerges from the ribosome and halts protein synthesis. The pause gives the ribosome time to bind to the srp-receptor. Prevents formation of a folded protein in the cytosol. The ribosome binds to a protein translocator that transfers the growing polypeptide chain across the membrane. The protein passes through an aqueous pore in the translocator.
