BIOL 205 Lecture Notes - Lecture 27: Cytosol, Sulfation, Ubiquitin
Document Summary
Rough er (aka rer) - the cytosolic surface of the membranes have attached ribosomes that are synthesizing proteins for import into the er. This is site of synthesis for proteins destined for secretion, lysosomes, or membranes. Smooth er (ser) is continuous with rough er as shown in the photo below, and is the site of lipid and steroid synthesis. The initial stages of protein processing involving folding of the protein into its 3d structure. Remember that folding of proteins takes place through interaction with chaperone proteins (refer to your notes from unit 2 if you need a refresher). Proteins that are not properly folded are destroyed. In the cytosol compartment they are tagged with ubiquitin and then sent to proteasomes for destruction. Other forms of processing of cytosolic proteins involve Covalent modification (e. g. phosphorylation, methylation, acetylation), and. Cleavage of the initial protein product to produce a smaller active protein.
