Membrane_proteins_and_transport

Membrane_proteins_and_transport - - membranes can be...

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Membrane proteins The ‘mosaic’ component of the fluid mosaic model Functions include Transport Enzymes 3 types: integral, peripheral, lipid-anchored Signal transduction Attachment/recognition BIO 1140 – SLIDE 1 Fig. 5.1 Membrane proteins The ‘mosaic’ component of the fluid mosaic model Functions include Transport Enzymes 3 types: integral, peripheral, lipid-anchored Signal transduction Attachment/recognition BIO 1140 – SLIDE 2 Fig. 5.8 e.g. Na + ,K + -ATPase e.g. Electron transport chain e.g. ß-adrenoreceptor e.g. cadherins Integral membrane proteins Amphipathic with one or more hydrophobic regions Usually transmembrane (single or multipass) Transmembrane regions typically -helix of 20-30 hydrophobic aa residues BIO 1140 – SLIDE 3 Fig. 5.9 Fig. 5.10 - membranes can be covalently attached - in most cases proteins are less mobile than lipids -- proteins can be anchored to things inside and outside the cell - can lead to polarized cells ; protein composition can be different in the basilateral and . .. - embedded in the membrane and extended fully across, relatively rare to have it partway -- at least one domain that crosses the membrane - tends to be a hydrophobic region of the protein - made up of nonpolar residues - hydrophobic interactions hold them in membrane - not easy to get them out of the membrane - would have to use detergents to break up the membrane to extract these integral proteins - not easy to study -
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Peripheral membrane proteins Membrane-associated through non non-covalent covalent interactions Dynamic relationship with membrane Lipid-anchored membrane proteins Membrane-associated through covalent linkages to phospholipids Fatty-acid anchored Intracellular orientation GPI anchor (glycosylphosphatidylinositol) BIO 1140 – SLIDE 4 extracellular orientation can be cleaved with phospholipase C e.g. type IV carbonic anhydrase Fig. 4.13 Karp 2010 Thought exercise How can the different properties of membrane proteins be used to distinguish among integral, peripheral and GPI-linked (lipid- anchored) proteins experimentally? BIO 1140 – SLIDE 5 Movement across membranes Overview Importance of size, polarity/charge, gradient How? Pi t BIO 1140 – SLIDE 6 Passive transport Simple diffusion Facilitated diffusion Active transport Primary Secondary Fig. 5.12 - peripheral - very dynamic relationship - noncovalent interactions --- because attached with noncovalent - easy to knock off, eg. changing temp or pH - lipid-anchored - more difficult to remove because held by covalent interactions - fatty-acid anchored - GPI anchored - found on external side - removed by cleaving the anchor using enzyme (phopholipase C) -- selective removal
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Movement across membranes Overview Importance of size,
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This note was uploaded on 03/26/2012 for the course BIO 1140 taught by Professor Fenwick during the Winter '07 term at University of Ottawa.

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Membrane_proteins_and_transport - - membranes can be...

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