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Last Class: 1. Posttranscription regulation 2. Translation regulation 3. Cell membrane, phospholipids, cholesterol 4. Membrane protein, mobility, FRAP, FLIP . Carbohydrate layer (Glycocalyx) on the cell surface Protecting the cell surface from mechanical and chemical damage
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Last Class: 1. Posttranscription regulation 2. Translation regulation 3. Cell membrane, phospholipids, cholesterol 4. Membrane protein, mobility, FRAP, FLIP
Carbohydrate layer (Glycocalyx) on the cell surface Protecting the cell surface from mechanical and chemical damage Lymphocyte stained with ruthenium red
Summary membrane proteins and their anchoring models Methods to study membrane proteins, detergents diffusion, distribution, methods to study protein motion and distribution glycocalyx, proteoglycan
Membrane Transport of Small Molecules and the Electrical Properties of Membranes
Permeability of plasma membrane General principles I
Permeability of plasma membrane General principles II Permeability coefficient (cm/sec)
Membrane Transport Proteins Carrier Protein and Channel Protein
Transportation Models Passive and Active Transport Electrochemical and concentration gradient, membrane potential Carrier proteins: passive and active Channels: always passive
Electrochemical Gradient Is the combinatory effect of concentration gradient and membrane potentials
Ionophores can serve as channels and carriers for ions Example: A23187, calcium permeabilizing agent
Conformational change of a carrier protein Mediates passive transport Change is spontaneous and random, so dependent on concentration
3 ways of driving active transportation utilizing passive carriers • Coupled carriers • ATP-driven pumps • Light-driven pumps
3 types of carrier-mediated transport Coupled carriers
Coupled transportation of glucose and Na+ Cooperative binding of Na+ and glucose to the carrier. Outer surface, Na+ high concentration induces the high affinity of glucose to carrier
Transcellular transport Tight junction separates apical and basal/lateral spaces Apical: glucose and Na+ coupling; basal/lateral: glucose is passive, Na+ maintained by ATP-driven pump
Na+-K+ Pump, ATPase P-type transport ATPase (dependent on phosphorylation)
Calcium Pump ATP binding and hydrolysis can push calcium inside by bring N and P domain together
A typical Ion Channel 1. selectivity, 2. Gated (close and open)
The Structure of bacterial K+ channel Selectivity 10,000 fold over Na, although K+ 0.133nm, Na+ 0.095 nm
The Selectivity of bacterial K+ channel Carbonyl oxygens at selective filter
Gating Model of K+ channel Selectivity filter is fixed, the vestibule open and close like a diaphragm
Summary • Membrane transportation, carrier protein, channel protein • Active transportation, passive transportation • Carrier Proteins, coupled carriers, ATPases, Na+-K+ Pump • Gating mechanisms of Ion Channels, K+ channel selectivity
An electron micrograph of part of a live cell seen in cross section
Hypothetical schemes for the evolutionary origins of organelles
Topological relationships between compartments of the secretory and endocytic pathways in a eucaryotic cell
A schematic roadmap of protein traffic Red: gated transport Blue: transmembrane transport Green: vesicular transport
Two ways in which a sorting signal can be built into a protein • Signal sequence • Signal patch
The transport of molecules between the nucleus and the cytosol
The arrangement of nuclear pore complexes in the nuclear envelope
Possible paths for free diffusion through the nuclear pore complex
The function of a nuclear localization signal • Nuclear localization signal: NLS • Nuclear export signal: NES
The compartmentalization of Ran-GDP and Ran-GTP Ran-GAP: cytosol->Ran-GDP Ran-GEF: nucleus->Ran-GTP
A model for how GTP hydrolysis by Ran provides directionality for nuclear transport
A model for how Ran-GTP binding might cause nuclear import receptors to release their cargo