1. Membranes Part 2 Proteins - Pumps

2. Membrane Proteins Integral proteins – Transmembrane domains 25 aa  -helix  -barrel H-bonding of all amino & carbonyl groups Hydrophobic residues – G, A, L, I, V – Hydropathy calculations predict TM domains from protein sequence

3. Membrane Proteins Peripheral proteins – Acylation Farnesylation Myristoylation Palmitoylation – GPI anchor – Electrostatic interaction – Partial insertion – Association with integral protein

4. Transport Complexes

5. Control of Membrane Permeability Selective permeability of membranes Control of solute movement across membranes – Pumps "active transport" Require energy source to achieve movement – Carriers "passive transport" Movement of particles down concentration gradients result in conformational changes that can allow transport against gradient – Channels "selective passive transport" Opening and closing is regulated

6. Types of Membrane Pumps Energy SourcePumpSubstanceDistribution Light BacteriorhodopsinH+H+ Halobacteria HalorhodopsinCl - PhotoredoxH+H+ Photosynthetic organisms Redox potential Electron transport chain NADH oxidase H+H+ Mitochondria, bacteria Decarboxlyation Ion-transporting decarboxlyases Na + Bacteria Pyrophosphate H + -pyrophosphataseH+H+ Plant vacuoles, fungi, bacteria ATPTransport ATPases various ions Universal

7. Three Families of Transport ATPases ClassDistributionSubstrateFunctions F-typeBacteria, chloroplastH + ATP synthesis or mitochondriaATP driven H + pumping V-type Archaea, eukaryotic H + ATP driven H + pumping membranes P-typePlasma memb, ERNa, K, CaCation pumping ABCPlasma membraneVariousSolute transport Copyright 2008 by Saunders/Elsevier. All rights reserved.

8. Figs. 8-5, 8-7, 8-9 Three Families of Transport ATPases F-type ATPase P-type ATPase ABC transporter Copyright 2008 by Saunders/Elsevier. All rights reserved.

9. ATP-Driven Pumps PumpDistributionSubstrate 1  Function F0F1F0F1 Mitochondria, chloroplasts, bacteria, plasma membranes H+H+ ATP synthesis V0V1V0V1 eukaryotic endomembranesH+H+ ATP-driven H + pumping Na/K-ATPaseplasma membrane3 Na + for 2 K + Na/K gradient generation H/K – ATPasestomach & kidney cell plasma membranes 1 H + for 1 K + gastric & renal H secretion H-ATPaseplasma membrane in yeast, plants & protozoa 1 H + proton gradient CFTRrespiratory & pancreatic epithelial cell plasma membranes ATP, Cl - Cl - secretion MDR1Plasma membraneDrugs MDR2Liver apical membranePCFlippase, bile secretion

10. F and V family ATPases

11. Subcellular Distribution of F-type and V-type ATPases Fig. 1.2 Copyright 2008 by Saunders/Elsevier. All rights reserved.

12. P-type ATPase: Ca 2+ of the endoplasmic reticulum Fig. 8-7 Copyright 2008 by Saunders/Elsevier. All rights reserved.

13. Mechanism of the P-type Ca-pump Fig. 8-8 Copyright 2008 by Saunders/Elsevier. All rights reserved.

14. ABC Transporters PumpDistributionSubstrateFunctions MDR1Plasma membraneOrganics, drugsDrug secretion MDR2Liver plasma membranePhosphatidylcholineFlippase CFTRRespiratory, pancreas PMATP, Cl - Cl - secretion TAP1, 2ERAntigenic peptidesER/cytoplasm transport HisQMPBacterial PMHistidineHistidine uptake PstSCABBacterial PMPhosphatePhosphate uptake OppDFBCABacterial PMOligopeptidesPeptide uptake Copyright 2008 by Saunders/Elsevier. All rights reserved.

15. ABCs of ABC Transporters ATP Binding Cassette Walker A motif or P-loop – GXXGXGKS/T – Binds  PO 4 Walker B motif – GX 6-8  4 D – Binds Mg 2+

16. Figs. 8-9 and 8-10 ABC transporters: variations on a common theme Vitamin B12 transporter BtuC BtuD Copyright 2008 by Saunders/Elsevier. All rights reserved.

17. Crystal structure & proposed mechanism of the BtuCD vitamin B 12 ABC transporter Fig. 8-10 Copyright 2008 by Saunders/Elsevier. All rights reserved.

18. Multiple drug resistance of human tumors from over expression of MDR ABC transporter Fig. 8-11 Copyright 2008 by Saunders/Elsevier. All rights reserved.