Section 5 - BLG311 F2019 Cell Sorting copy.pptx - Section 5...

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Intracellular compartmentalizat ion and protein sorting Section 5: 1
Why do we care about protein sorting within cells?
2 Hartley et al. Mutations in TT37 cause trichohepatoenteric syndrome. Gastroenterology. 2010. 138: 2388-2398
Membrane organelles compartmentalize the cell 3
Why compartmentalize the cell? 1. membrane surface area more surface for membrane-based processes greater membrane area to cell volume ratio 2. segregates specialized functions: incompatible reactions (synthesis versus degradation) proteins coming into versus proteins going out of the cell storage sites acidic versus non-acidic environments 3. membrane-bound organelles have 3 distinct parts: a. The cytoplasmic face of the bilayer b. The luminal face of the bilayer c. the lumen 4
Membrane-bound organelles are specialized compartments Plasma membrane : controls intake and exit from the cell; communicates with the extracellular medium and with other cells Nucleus : A double bilayer organelle that encloses and protects DNA and controls gene expression Mitochondria: oxidation of energy molecules to make ATP Chloroplasts: photosynthesis: conversion of light into chemical energy 5 Peroxisomes : reduction-oxidation reactions Endosomes: sorts proteins for recycling or degradation Lysosomes: Degradation of membranes and proteins Endoplasmic reticulum : biosynthesis of lipids and proteins Golgi apparatus: Processing of proteins and lipids; sorting and transport to different parts of the cell
6 What causes organelles specialization? Organelle 1 Organelle 2
Three important facts about organelle function 7 1. Each organelle has a specific set of functions 2. Each specialized function requires a specific set of proteins and lipids 3. Organelles are not isolated: they exchange content So…. how are specific proteins targeted and transported to specific organelles?
Protein have a build-in signal that tells them where to go Günter Blobel, 1999 Nobel prize in Physiology or Medicine, “ for the discovery that proteins have intrinsic signals that govern their transport and localization in the cell” KDEL Endoplasmic reticulum Send to Acidic cluster Trans-Golgi network Yxx f Internal organelles D/ExxLL Lysosome 8
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