Biology 2581B Study Guide - Quiz Guide: Sec61, Signal Peptidase, Lipid Bilayer
2 May 2020
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Document Summary
Er proteins are of two different types: transmembrane proteins: are only partly translocated across the er membrane and become embedded in it. Some of these stay in the er, others are destined to reside in the membrane of another organelle: water-soluble proteins: are fully translated across the er membrane and then released into the er lumen. Some of these stay in the er lumen, others are destined for secretion or residence in lumen of other organelles. Er resident proteins contain a special er retention signal of four amino acids which is responsible for retaining the protein in the er. They also work as catalyst to fold the protein correctly after translocation. The core of the translocator in the er membrane is called the sec61 complex. This complex is built from 3 subunits containing helices that contribute to the formation of a central water channel through which the polypeptide chain traverses the membrane.
