Long answer Flashcards
Describe the structural features of a transmembrane domain (TMD). For a type II membrane protein, describe the process of its insertion into the membrane including the role of the TMD.
the structural features of a transmembrane domain do not contain a signal sequence
(a) Define a nuclear export signal. (b) Describe the steps involved in the export of a protein containing a NES out of the nucleus. Be sure to include the role of any required GTP-binding proteins.
a) Definition of a nuclear export signal = specific stretch/sequence of amino acids that are recognized by exportin and serve as a ZIP CODE to mediate targeting of the protein from the nucleus to the cytosol. Most common NES consists of a leucine-based motif
b) Importin alpha binds to exportin which mediates nuclear to cytosol transport
- (a) Name the G-protein that is primarily responsible for regulating COPII transport vesicle formation at the endoplasmic reticulum. (b) Describe how this G-protein does this.
a) COPII is the coated vesicles that move ‘forwards’ from the ERES to the Golgi
The G-protein responsible for the regulation of COPII transport is Sar1-GDP/GTP and is recruited from the cytosolic surface of the ERES
b) It does this by the Sar1-GDP binding to Sec12 GEF which generates Sar1-GTP
The Sar1-GTP integrates into the ER outer leaflet at the ERES causing the membrane curvature of the ERES membrane
- Outline the key steps in N-linked glycosylation of a protein in the endoplasmic reticulum.
N-Linked Glycosylation is when an oligosaccharide is added to the amino group on the side chain of an asparagine. It consists of two stages core glycosylation and core modification
- Describe the steps involved in one of the two unfolded protein response pathways discussed in class.
UPR Pathway Activated due to ER-Stress [PERK-mediated UPR pathway]
- Describe the steps that take place to retrieve a soluble endoplasmic reticulum-resident protein from the cis-Golgi back to the ER. Identify at least one sorting signal.
idk
- Discuss how both soluble and membrane-bound resident endoplasmic reticulum (ER) proteins are recognized at the cis Golgi network and ‘recycled’ back to the ER.
idk
- Describe the steps involved in the targeting and transport of a lysosomal hydrolase from the Golgi complex to the lysosome. Name the type of transport vesicle involved (you do not need to describe the formation of the vesicle coat).
- In the TGN soluble M6P-bearing lysosomal proteins are recognized by the M6P receptor which mediates the subsequent concentration of lysosomal proteins into newly synthesized clathrin coated vesicles.
- GRASPs and golgins are types of proteins that are essential for the maintenance of Golgi structure. For each of these, identify the role played in Golgi structure and describe the consequences of the protein not being expressed.
GRASPS = GRASPs serve as tethering proteins to link different Golgi sub compartments together
Depletion of GRASPs would result in the disassembly of the Golgi complex
GOLGINS = are long filamentous proteins that tether parts of the Golgi to the cytoskeleton and other subcellular structure. Disorganization Golgi due to lack of solid interaction with the cytoskeleton
- Describe the steps involved in receptor-mediated endocytosis of a plasma membrane receptor protein and its bound, extracellular ligand. Include in your answer the steps up to recycling of the receptor back to the plasma membrane and delivery of the ligand to the lysosome.
- PM transmembrane receptor become activated by binding to a specific soluble extracellular ligand
- Describe the structure of clathrin. With specific reference to its structure, describe how clathrin functions as a coat protein.
Clathrins is made of three light chain polypeptides and three heavy chain polypeptides forming a triskelion. The triskelions are what form the outer scaffolding of the coat on the growing vesicle.
It functions as a coat protein by the lattice assembly promoting the bending of the membrane forming hexagons which lie flat on the membrane surface. Triskelions will then begin to form pentagons rather than hexagons to act as the driving force for membrane curvature
- Describe the steps involved in mitochondrial fission or fusion
fission = 3
fusion = 2
- Describe the steps involved in the targeting and import of a soluble protein into the mitochondrial matrix.
- In the cytosol, newly synthesized protein is recognized by cytosolic chaperones
These chaperones control the overall conformation of the matrix - destined protein - maintain the nascent protein in a partially unfolded, import-competent state using ATP
Nascent mitochondrial proteins are enriched in the vicinity of the mitochondrial surface due to diffusion and mRNA localization
- Describe the steps involved in the targeting and import of a soluble protein into the chloroplast stroma and its subsequent targeting into the thylakoid lumen by the pH dependent pathway
- Transport into the stroma is highly analogous to transport into the mitochondrial matrix
