BIOLOGY 2B03 Lecture Notes - Lecture 5: Pex5, Integral Membrane Protein, Translocon
27 Sep 2016
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Document Summary
16-30 n-terminal residues containing a: short positively charged domain, central hydrophobic domain, polar c- terminal domain. Er signal sequence on protein being synthesized directs ribosome to er membrane. Cytosolic ribonucleoprotein particle is composed of 6 proteins and. N-terminal 18-50 amino acids amphipathic helix: hydrophobic aa on one side, and positively-charged basic aa on other helix side. Pts1 = ser-lys-leu or skl at extreme c-terminus. Pts2 used by some peroxisomal proteins at n- Hydrophobic face of amphipathic helix interacts with hydrophobic pocket of receptor. Cytosolic protein pex5 recognizes pts1 via tpr motif. Tpr 2 alpha helices connected by loop. Subunit of srp receptor interacts with srp/nascent chain/ribosome complex. Interaction is dependent on gtp binding to srp and. Srp and srp receptor ( ) powers transfer of nascent chain and ribosome to translocon. Dissociation of srp and srp receptor dissociation of srp allows translational to continue. Polypeptide passes through translocon into er lumen, signal peptidase cleaves off signal sequence.
