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#ER

2 public questions tagged with this topic.

Basics of Cell Biology

Which of the following statements about endoplasmic reticulum is false?

Endoplasmic reticulum is continuous reticulum of sheets and tubules emanating from outer nuclear membrane, enclosing single lumen bounded by phospholipid bilayer containing translocon Sec61 for cotranslational import. Rough ER domain densely studded with 80S ribosomes docking via SRP receptor synthesizes secretory and membrane proteins that fold aided by chaperone BiP, protein disulfide isomerase PDI forming disulfides, and undergo initial N-glycosylation by oligosaccharyltransferase. Smooth ER abundant in hepatocytes and steroidogenic cells lacks ribosomes, houses lipid synthesis enzymes incl

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 12: Endoplasmic Reticulum Organization.

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Protein Sorting and Trafficking

Which of the following recognizes the signal sequence of nascent proteins targeting the ER?

Early sorting of nascent secretory and membrane proteins is performed by signal recognition particle, conserved ribonucleoprotein containing 7SL RNA scaffold and six protein subunits. When hydrophobic signal sequence of about eight to twelve non-polar residues emerges from ribosomal exit tunnel, methionine-rich M domain of SRP54 forms flexible hydrophobic groove whose abundance of sulfur-containing methionine side chains allows plastic accommodation of diverse signal sequences via induced fit. Binding is communicated through 7SL RNA to Alu domain comprised of SRP9 and SRP14 heterodimer that do

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 13: SRP Recognizes Signal Sequences.

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