MCB Test 1 Mueckler Review

Transcription

1 MCB Test 1 Mueckler Review

2 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

3 FaJy Acid SaturaHon

4 Bilayers are Thermodynamically Stable Structures Formed from Amphathic Lipids (Hydrophobic) (Hydrophilic) Figure 10-11a Molecular Biology of the Cell ( Garland Science 2008)

5 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

6 PhosphoLipid Movements within Bilayers (µm/sec) ( /sec) ( /sec) Figure 10-11b Molecular Biology of the Cell ( Garland Science 2008)

7 Figure Molecular Biology of the Cell ( Garland Science 2008) A Scramblase Enzyme Catalyzes Symmetric Growth of Both Leaflets in the ER

8 A Flippase Enzyme promotes Lipid Asymmetry in the Plasma Membrane Figure Molecular Biology of the Cell ( Garland Science 2008)

9 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)

10 2. Phospholipases Produce Signaling Molecules via the Degrada%on of Phospholipids

11 Cholesterol Biosynthesis Occurs in the Cytosol and at the ER Membrane Through Isoprenoid Intermediates (Rate-LimiHng Step in ER)

12 3 Ways in which Lipids May be Transferred Between Different Intracellular Compartments Vesicle Fusion Direct Protein-Mediated Soluble Lipid Transfer Binding Proteins

13 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 Molecular Biology of the Cell ( Garland Science 2008)

14 Membrane Domains are Inside-Out Right-Side Out Soluble Protein Figure 3-5 Molecular Biology of the Cell ( Garland Science 2008)

15 Figure 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

16 4 Ways that Protein Mobility is Restricted in Biological Membranes Intramembrane Protein- Protein InteracHons InteracHon with the cytoskeleton InteracHon with the extracellular maxtrix Figure Molecular Biology of the Cell ( Garland Science 2008) Intercellular Protein-Protein InteracHons

17 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)

18 Signal-Mediated Targe%ng to the RER

19 Proper%es of Secretory Signal Sequences 8-12 Residues cleavage N ++ Hydrophobic Core Mature Protein Residues Located at N-terminus Residues in length Hydrophobic core of 8-12 residues OZen basic residues at N-terminus (Arg, Lys) No sequence similarity

20 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

21 In Vitro Transla%on/Transloca%on System mrna + TranslaHon Components + Amino acid* Protein* SDS PAGE

22 In Vitro Transla%on of Prolac%n mrna ProlacHn is a polypephde hormone (MW ~ 22 kd) secreted by anterior pituitary MW (kd) SDS Gel 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

23 Mul%pass Topologies are Generated by Mul%ple Internal Signal/Anchor Sequences Type IVa Figure Molecular Biology of the Cell ( Garland Science 2008)

24 The Charge Difference Rule for Mul%spanning Membrane Proteins COOH NH COOH + NH 2 + cytoplasm NH COOH NH 2 + COOH + cytoplasm

25 Oligosaccharide Processing in the RER is Used for Quality Control Figure Molecular Biology of the Cell ( Garland Science 2008)

26 Disulfide Bridges are Formed in the RER by Protein Disulfide Isomerase (PDI)

27 Proteins are Incorporated Into Mitochondria Via Several Different Routes Figure Molecular Biology of the Cell ( Garland Science 2008)

28 Protein Import into the Matrix Requires ATP Hydrolysis and an Intact Proton Gradient Across the Inner Membrane Figure Molecular Biology of the Cell ( Garland Science 2008)

29 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

30 Targe%ng to the Intermembranous Space Occurs Via Two Dis%nct Pathways IM Space Protease Direct Delivery Cytochrome B2 Cytochrome c Heme Lyase

31 Targe%ng to the Outer Membrane Via the SAM Protein Complex (SorHng and Assembly Machinery) (β-barrell) Figure Molecular Biology of the Cell ( Garland Science 2008)

32 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)

33 Nuclear Import and Export Sequences are Recognized by Different Members of the Same Receptor Family (Keryopherins) Figure Molecular Biology of the Cell ( Garland Science 2008)

34 Nuclear Import and Export Operate Via Reciprocal Use of the Ran-GDP/GTP Concentra%on Gradient Figure Molecular Biology of the Cell ( Garland Science 2008)