Into membrane so that the N-terminus of the protein is exoplasmic. Describe two mechanisms for cotranslational insertion of a single-pass protein.Describe a model that would account for the cotranslational insertion ofĪ single-pass protein into membrane so that the N-terminus of the protein.If a single-pass membrane protein has an internal signal sequence, whatĭetermines whether the N-terminus of the mature protein will be cytosolic.What is "BiP"? Describe the role of BiP in posttranslational insertion.(Indicate the names of the "motor" proteins or protein complexes for each case.) Compare general modes of action of the "motors" used by eukaryotic systems and bacterial systems for posttranslational translocation of proteins across the ER membrane (eukaryotes) and the cytoplasmic membrane(bacteria).Types of factors determine which role will be played by a translocon at any Proteins into the ER lumen, posttranslational insertion of proteins into theĮR lumen, and elimination of improperly folded proteins from the ER, what Given that the Sec61 complex participates in cotranslational insertion of.In the ER lumen:(a) calnexin, (b) protein disulfide isomerase, and (c) glycosyl Describe the roles of each of the following in "quality control" of glycoproteins.Describe the roles of calnexin and calreticulin in preventing prematureĪggregation of segments of nascent glycoproteins during their translational.Describe the general role of dolichol in the formation of an oligosaccharideĬhain that will be attached to the side chain of an asparagine.Of many proteins translated by ribosomes of the RER. Indicate the role of protein disulfide isomerase (PDI) in the correct folding.Explain the role of disulfide bonds in the folding of many proteins entering.Is this model relevant to the insertion of membrane-spanning sequences of integral membrane proteins into membrane? Describe briefly the most recent model (based on X-ray data) for how the signal sequence is released form the translocon.What factors are believed to displace the "plug" in the protein translocating channel and allow transfer of proteins to the ER lumen?.In protien translocation does not form an open channel from the ER lumen to What is the nature of the "plug" that insures that a translocon not engaged.Which subunit of the Sec61 complex forms the protein translocation channel of the translocon? How would we know this simply by looking at the structurs of the Sec61 subunits?.What is the Sec61 complex of eukaryotes?.Of the fact that SRP pauses translation when it binds to a signal peptide See if you can design an experiment that would demonstrate the importance.What is the role of the "signal peptidase"?.Expalin briefly why hydrolysis of GTP on the SRP and the SRP receptor mightĬause SRP to release from the signal sequence and from its receptor.Describe briefly the current view of how SRP binding to its ER receptor positions the signal sequence for insertion into the translocon.How does binding of SRP to the signal sequence of a nascent protein.Explain briefly why it is important that SRP binding to the signal sequence.Describe the role(s) of the SRP in positioning the ribosome-nascent protein.Post-translational insertion of a secretory protein into the RER (or microsomes!). Describe an experiment that would distinguish between co-translational and.Inserted into the ER lumen cotranslationally reaches the ER. Describe the process by which a ribosome destined to synthesize a protein.Describe the essential feature of the signal sequence of proteins inserted.What sorts of proteins are synthesized by polysomes bound to the endoplasmic.What sorts of proteins are synthesized entirely on free cytosolic polysomes?.Protein Synthesis and the Secretory Pathway: RER
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