BIOMEMBRANES
István Léránt
BIOMEMBRANES
Barriers
Define the inside and the outside of
the cells
Sheetlike structures
Closed bounderies
Specific proteins serve as
Pumps
Channels
Receptors
Energy transducers
A biomembránok felépítése
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Comparision of various types of
membranes
[%]
Lipids
Proteins
Carbohydrates
Hepatocyta m.
75
20
5
Myelin
39
54
7
Sarcoplasmic ret.
32
64
4
Mit. – outer m.
46
50
4
Mit. – inner m
23
75
2
as a % of the total mass
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• Membranes consist maily of
MEMBRANES
Barriers
Define the inside and the outside of
the cells
Sheetlike structures
Closed bounderies
Specific proteins serve as
Pumps
Channels
Receptors
Energy transducers
–
–
–
–
Lipids
Proteins
1:1 ratio (1:4 -> 4:1)
Carbohydrates
• Glycolipids
• Glycoproteins
• Lipid bilayer - barrier
• Hydrophylic & hydrophobic
sidechains
• Specific proteins as
– Pumps
– channels
– Receptors
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Comparision of various lipid compoments
Neutral lipids
Membran lipids
Structure – form.
Phospholipids
Triacylglycerols
Energy stores
Glyerol
Fatty cid(2)
Fatty cid(3)
Glycerol
Fatty cid(1)
Fatty cid(1)
Fatty cid(2)
Cholesterol
Glycolipids
sphingosine
sphingosine
Fatty acid
Fatty acud
HO
P
Alcohol
P Choline
Glu / Gal
Ceramide
Phospholipids
Glycoproteins
Specific function
BIOMEMBRANES
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Steroidal hormones
Eicosanoids
Vitamins (A, D, E, K)
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Phosphatidic acid
MEMBRANES
PHOSPHOLIPIDS
PHOSPHOGLYCERIDES
Sphingolipids - sphingomyelin
Sn-1 – Fatty acid
Sn-2 – Fatty acid – usually unsaturated, polyunsaturated
‘alcohol’ – choline
ethanolamine
serine
inositol
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MEMBRANES
PHOSPHOLIPIDS
PHOSPHOGLYCERIDES
Sphingolipids - sphingomyelin
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Digestion of phospholipids by
Specific phospholipase enzymes
phospholipase A1
phospholipase A2
Lysophospholipid
X
phospholipase C
phospholipase D
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víz
Polar
component
phosphate
„head” hydrophyl
Glycerol
„Tail” hydrophob
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MEMBRANES
PHOSPHOLIPIDS
PHOSPHOGLYCERIDES
Sphingolipids - sphingomyelin
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A sphingomyeline
H
3
H
O
2
CH CH C
O
H
C
1
CH2
+
N
H2
C R
Fatty acids
O
O P O
O
Sphingosine Ceramide
Choline
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CH3
+
CH2 CH2 N
CH3
CH3
Phosphoric acid
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Glycolipids
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MEMBRANES
• Lipid bilayer
• Phospholipid, cholesterol
ration
– Type of membrane
HO
• Dual influence of
cholesterol
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MEMBRANES
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IN VITRO – PREPARATION
OF LIPOSOMES
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IN VITRO – PREPARATION
OF LIPOSOMES
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IN VITRO – PREPARATION
OF LIPOSOMES
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• Outer layer
IN VITRO – PREPARATION
OF LIPOSOMES
MEMBRÁNOK ASSZIMETRIÁJA
– phosphatidylcholine
– Sphingomyelin
• Inner layer
– phosphatidylethanolamine
– phosphatidylserine
• Lipid movement in
membranes
– Rotation
– Lateral diffusion
– Flip-flop
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Rapid diffusion of
memberan lipids and
proteins
Membran compoment is labelled by
fluorescent dye
~ 3 mm2 surface area
-Bleaching
• Flourescence recovery after
photobleaching (FRAP)
• Fluorescence Recovery After
Photobleaching (FRAP)
Lateral mobility D
S  4Dt 
1
2
where D  diffusion coefficent
The average distance ' S' traversed in time t depends on D
D lipid 1 mm 2s -1 D phospholipid 2 mm 2s -1
Protein movement
protein / lipids similar mobility
photorecep tor rhodopsin 0,4 mm 2s -1
fibronecti n 10 -4 mm 2s -1
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MEMBRAN PROTEINS
Way of isolation:
Periferial membrane proteins
pH changement
Salt concentration
Integral membrane proteins
Intensive treatment
Detergents
Organic solvents
Hyrophobic, transmembrane domain
(~ 25 hydrophobic amino acids)
Integral (a,b,c) and peripherial (d,e) membrane proteins
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Structure of bacteriorhodopsine
a-hélix
Citoplazma
felőli nézet
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Covalently bound proteins
Palmityl-group – HS-Cys THIOESTER
C terminal Cys -. Farnesyl-group
GPI – ancor (glycosyl-phosphatydilinositol) (enthanol-amin – P –
mannose, GlcNac –
Glycosylphosphatydilinositol GPI)
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SINGER-NICHOLSON
MODEL
Two dimensional solution of
membrane – lipids and globular
proteins
Solvent of integral proteins
Lateral diffusion of protein is free
Permeability barrier
• Lipid bilayer
• Integral – transzmembrane
- proteins
• Membrane
– Lipid bilayer
– Glycolipids (‘-’ charge)
• Internal peripherial
proteins
• Fluid-mosaic model
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LIPIDS OF
BIOMEMBRANES
Phospholipids
Glycolipids
Cholesterol
Stearinic acid octadecanoic acid, 18: 0
Oleic acid, cis-9-octadecenoic acid cis 18:1
Linolic, cis, cis-9,12-octadecadienoic acid cis,cis 18:2
COOH
H3C
Olvadáspont: 69,6 oC
H
COOH
H3C
Olvadáspont: 52 oC
Sztearinsav
H
H
Tr ansz
H
COOH
16 ofelépítése
C
AOlvadáspont:
biomembránok
Elaidinsav
Ci sz
Olajsav
27
Membrane fluidity and
unsaturated fatty acids +
cholesterol
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Membran functions
Signaltransduction
Signal transformation
Structure of membranes
Barriers
Define the inside and the outside of
the cells
Sheetlike structures
Closed bounderies
Specific proteins serve as
Pumps
Channels
Receptors
Energy transducers
Signaltransduction
Answer
Second
mesengers
Hormons
External
signals
Receptor
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Biochemical
changement
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