MCB Test 1 Mueckler Review 9-30-17
Func%ons of Cellular Membranes 1. Plasma membrane acts as a selec%vely permeable barrier to the environment Uptake of nutrients Waste disposal Maintains intracellular ionic milieu 2. Plasma membrane facilitates communica%on With the environment With other cells 3. Intracellular membranes allow compartmentaliza%on and separa%on of different chemical reac%on pathways Increased efficiency through proximity Prevent fuhle cycling through separahon Protein secrehon
FaJy Acid SaturaHon
Bilayers are Thermodynamically Stable Structures Formed from Amphathic Lipids (Hydrophobic) (Hydrophilic) Figure 10-11a Molecular Biology of the Cell ( Garland Science 2008)
Figure 10-8 Molecular Biology of the Cell ( Garland Science 2008) The Forma%on of Cell-Like Spherical Water-Filled Bilayers is Energe%cally Favorable
PhosphoLipid Movements within Bilayers (µm/sec) (10 12-10 13 /sec) (10 8-10 9 /sec) Figure 10-11b Molecular Biology of the Cell ( Garland Science 2008)
Figure 12-58 Molecular Biology of the Cell ( Garland Science 2008) A Scramblase Enzyme Catalyzes Symmetric Growth of Both Leaflets in the ER
A Flippase Enzyme promotes Lipid Asymmetry in the Plasma Membrane Figure 12-58 Molecular Biology of the Cell ( Garland Science 2008)
Phospholipids are Involved in Signal Transduc%on 1. Ac%va%on of Lipid Kinases PI-4,5P PI-3,4,5P Figure 10-17a Molecular Biology of the Cell ( Garland Science 2008)
2. Phospholipases Produce Signaling Molecules via the Degrada%on of Phospholipids
Cholesterol Biosynthesis Occurs in the Cytosol and at the ER Membrane Through Isoprenoid Intermediates (Rate-LimiHng Step in ER)
3 Ways in which Lipids May be Transferred Between Different Intracellular Compartments Vesicle Fusion Direct Protein-Mediated Soluble Lipid Transfer Binding Proteins
The 3 Basic Categories of Membrane Protein GPI Anchor Single-Pass Mul%-pass β-strands Transmembrane Helix Linker Domain Fa_y acyl anchor Integral Lipid- Anchored Peripheral (can also interact via PL headgroups) Figure 10-19 Molecular Biology of the Cell ( Garland Science 2008)
Membrane Domains are Inside-Out Right-Side Out Soluble Protein Figure 3-5 Molecular Biology of the Cell ( Garland Science 2008)
Figure 10-31 Molecular Biology of the Cell ( Garland Science 2008) Func%onal Characteriza%on of Integral Membrane Proteins Requires Solubiliza%on and Subsequent Recons%tu%on into a Lipid Bilayer
4 Ways that Protein Mobility is Restricted in Biological Membranes Intramembrane Protein- Protein InteracHons InteracHon with the cytoskeleton InteracHon with the extracellular maxtrix Figure 10-39 Molecular Biology of the Cell ( Garland Science 2008) Intercellular Protein-Protein InteracHons
Ribosomal Subunits are Shared Between Free and Membrane-Bound Polysomes Targe&ng informa&on resides in the Nascent polypep&de chain Figure 12-41a Molecular Biology of the Cell ( Garland Science 2008)
Signal-Mediated Targe%ng to the RER
Proper%es of Secretory Signal Sequences 8-12 Residues cleavage N ++ Hydrophobic Core Mature Protein 15-30 Residues Located at N-terminus 15-30 Residues in length Hydrophobic core of 8-12 residues OZen basic residues at N-terminus (Arg, Lys) No sequence similarity
In Vitro Transla%on/Transloca%on mrna Rough microsomes Ribosomes trnas System Soluble translahon factors Low MW components Energy (ATP, creahne-p, creahne kinase) ReHculocyte or wheat germ lysate
In Vitro Transla%on/Transloca%on System mrna + TranslaHon Components + Amino acid* Protein* SDS PAGE
In Vitro Transla%on of Prolac%n mrna ProlacHn is a polypephde hormone (MW ~ 22 kd) secreted by anterior pituitary MW (kd) 25 22 18 SDS Gel 1 2 3 4 5 6 7 8 Lanes: 1. Purified prolachn 2. No RM 3. RM 4. No RM /digest with Protease 5. RM /digest with Protease 6. RM /detergent treat and add Protease 7. ProlacHn mrna minus SS + RM /digest with Protease 8. SS-globin mrna + RM / digest with Protease
Mul%pass Topologies are Generated by Mul%ple Internal Signal/Anchor Sequences Type IVa + + + + Figure 12-48 Molecular Biology of the Cell ( Garland Science 2008)
The Charge Difference Rule for Mul%spanning Membrane Proteins COOH NH 2 + + COOH + NH 2 + cytoplasm NH 2 + + COOH NH 2 + COOH + cytoplasm
Oligosaccharide Processing in the RER is Used for Quality Control Figure 12-53 Molecular Biology of the Cell ( Garland Science 2008)
Disulfide Bridges are Formed in the RER by Protein Disulfide Isomerase (PDI)
Proteins are Incorporated Into Mitochondria Via Several Different Routes Figure 12-23 Molecular Biology of the Cell ( Garland Science 2008)
Protein Import into the Matrix Requires ATP Hydrolysis and an Intact Proton Gradient Across the Inner Membrane Figure 12-26 Molecular Biology of the Cell ( Garland Science 2008)
Targe%ng to the Inner Membrane Occurs Via 3 Dis%nct Routes Stop-Transfer-Mediated Oxa1-Mediated Tom70/Tim22/54-Mediated Single-Pass Proteins Cytochrome oxidase subunit CoxVa ATP Synthase Subunit 9 Mul%-Pass Proteins ADP/ATP An%porter
Targe%ng to the Intermembranous Space Occurs Via Two Dis%nct Pathways IM Space Protease Direct Delivery Cytochrome B2 Cytochrome c Heme Lyase
Targe%ng to the Outer Membrane Via the SAM Protein Complex (SorHng and Assembly Machinery) (β-barrell) Figure 12-27 Molecular Biology of the Cell ( Garland Science 2008)
Nuclear Transport Bidirec%onal Single Large Pore Complex Spans 2 lipid bilayers Nuclear Pores much larger than other translocons Figure 12-8 Molecular Biology of the Cell ( Garland Science 2008)
Nuclear Import and Export Sequences are Recognized by Different Members of the Same Receptor Family (Keryopherins) Figure 12-13 Molecular Biology of the Cell ( Garland Science 2008)
Nuclear Import and Export Operate Via Reciprocal Use of the Ran-GDP/GTP Concentra%on Gradient Figure 12-15 Molecular Biology of the Cell ( Garland Science 2008)