BIOL 201 Lecture Notes - Lecture 20: Translocon, Ldl Receptor, Alpha Helix
Document Summary
There is a constant flow and trafficking between the endomembrane systems: for example: how did the ldl receptor end up imbedded in the membrane. Implies that there is a mechanism for marking the vesicles and filling them with the right product. Occurs via signal sequences: part of polypeptide at the n-terminus of the gene created by ribosomes that targets it to a location in the cell. Causes cell to ship to correct location. Specific example for today: getting into the lumen of the er: these proteins are often translated by ribosomes bound to the er, output of ribosome fed directly into the er lumen as translation occurs via translocon. Mrna starts translation in the cytoplasm: n-terminus of polypeptide is very hydrophobic and has characteristic sequences, recognized by proteins which are specific to the characteristic hydrophobic sequence. Binds to nascent protein and the ribosome. Signal sequence is now imbedded in the signal recognition protein (srp)