Membrane Protiens Flashcards
What evidence is there that proteins are present in membranes?
Functional proof=facilitated diffusion, ion grads, specific cell responses
Biochemical (experiment) proof=membrane fractionation+gel electrophoresis, freeze fracture
How does freeze fracture show a cells membrane?
It doe this as when the ice crystal is broken it breaks along a line of weakness. In a frozen cell this is between the bilayer.
How do proteins move in by layers?
Conformational change (signaling etc)
Rotational
Lateral
No flip flop (thermodynamically challenging, important as ensures receptors remain on the correct side of the membrane)
What restricts the way proteins move in a bylayer?
Proteins aggregate together_a larger mass to move
Proteins are tethered to ECM or cytoskeleton_fixed to a point
Proteins interact with proteins on next cell_hold protein and cell in place
Lipid mediated effects-proteins separate into flip phase or cholesterol poor regions
What makes a membrane protein peripheral?
It’s bound to the surface
Sits on the membrane via hydrostatic or H bond reactions-washes off with salt solution
Can be removed by changes in pH or ionic strength
What makes a membrane protein integral?
Interact extensively with hydrophobic domain of lipid bylayer
Cannot be removed by manipulation pH Orion strength
Only removed by agents that compete for the non-polar interactions (detergent or organic solvent)
What is a key characteristic of the amino acids that reside in the bilayer in transmembrane proteins?.
That are largely hydrophobic
Often a-helical
What is membrane protein topology?
It’s the orientation of the protein.
They always sit the same way in the membrane so that receptors etc are in the correct position.
Give two examples of haemolytic anaemia and gives me basic inf about each.
Hereditary Spherocytosis =
Spectrin depleted by 40-50% so lattices more open
Less resistant to lysis(struggle fit capillary)
Cleared by spleen
Hereditary elliptocytosis=
Defection in spectrin molecule (rugby ball shape)
Unable to form heterotramers
Fragile elliptoid cells
LOOK AT SLIDES FOR HOW PROETIN GETS INTO THE MEMBRANE
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