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

Diagram of glycocalyx

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

Carrier Proteins and Active Membrane Transportation

Conformational change of a carrier protein Mediates passive transport Change is spontaneous and random, so dependent on concentration

Kinetics of simple and carrier-mediated diffusions

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

P-type transport ATPase (dependent on phosphorylation) Na+-K+ Pump, ATPase P-type transport ATPase (dependent on phosphorylation)

Cycles of Na+-K+ Pump

Calcium Pump ATP binding and hydrolysis can push calcium inside by bring N and P domain together

1. selectivity, 2. Gated (close and open) A typical Ion Channel 1. selectivity, 2. Gated (close and open)

The gating of Ion Channels

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

Intracellular Compartments and Protein Sorting

The major intracellular compartments of an animal cell

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

Vesicle budding and fusion during 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 nuclear envelope

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

Nuclear import receptors

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

The control of nuclear import during T-cell activation

The endoplasmic reticulum

Fluorescent micrographs of the endoplasmic reticulum

The rough ER

Free and membrane-bound ribosomes

The Isolation of purified rough and smooth microsomes from the ER

The signal hypothesis

The signal-recognition particle (SRP)

How ER signal sequences and SRP direct ribosomes to the ER membrane

Evidence for a continuous aqueous pore joining the ER lumen and the interior of the ribosome

Three ways in which protein translocation can be driven through structurally similar translocators

A model for how a soluble protein is translocated across the ER membrane

How a single-pass transmembrane protein with a cleaved ER signal sequence is integrated into the ER membrane

Integration of a single-pass membrane protein with an internal signal sequence into the ER membrane

Integration of a double-pass membrane protein with an internal signal sequence into the ER membrane

The insertion of the multipass membrane protein rhodopsin into the ER membrane

The asparagine-linked (N-linked) precursor oligosaccharide that is added to most proteins in the rough ER membrane

Protein glycosylation in the rough ER

The role of N-linked glycosylation in ER protein folding Calnexin: membrane-bound chaperone protein Calreticulin: soluble chaperone protein

The export and degradation of misfolded ER proteins

The unfolded protein response in yeast

The attachment of a GPI anchor to a protein in the ER

The synthesis of phosphatidylcholine

The role of phospholipid translocation in lipid bilayer synthesis

Phospholipid exchange proteins

Summary Nucleus translocation, NLS, NES, nuclear pore complex, Ran-GTP Endoplasmic reticulum, rough ER, smooth ER, SRP, soluble and membrane proteins in ER, Glycosylation in ER, folding, Membrane lipid bilayer assembly