College aantekeningen
Biomolecular Architectures notes part 2
Detailed notes followed by pictures and tables on all of the lectures for the 'Biomolecular architectures' course
[Meer zien]Voorbeeld 3 van de 21 pagina's
Voorbeeld 3 van de 21 pagina's
In winkelwagengesponsord bericht van onze partner
Verkoper
Volgen
Voorbeeld van de inhoud
MEMBRANE-BASED ARCHITECTURES1. lipid bilayer
− functions:
o containment – separating the intracellular from the extracellular environment
o meeting platform – receiving and transducing extracellular signals
o compartmentalization – lipids and proteins are organized in ordered areas to increase
signalling efficiency
o mechanosensing – membrane invaginations are formed or flattened depending on
mechanical stimuli
− composition:
o mix of various lipid types: cholesterol, cardiolipids, sphingolipids…
o type and location of lipids → keep the biological functions of the protein
o asymmetrical bilayer
o mix of proteins with different properties → posttranslational modifications are
responsible for keeping proteins in a lipid environment
o nanoscale architectures and organizations within the cell membrane → not a fluid
mosaic
− phase separation of lipids:
o liquid-ordered state LO – below physiological temperature
o liquid-disordered state LD – above physiological temperature
o LO long chain saturated fatty acids & LD kinked unsaturated fatty acids – at physiological
temperature
o cholesterol likes to fit in
between the ordered
structures (small polar head)
with more complex
glycosylated heads →
ordered domain that will be
between the disordered ones
o phase separation can change
depending on several factors: pH, cholesterol, temperature, chemical modifications of
the components
o cholesterol sulphate has a stabilizing role in cell membranes which can change the
curvature of the membrane (cholesterol vs. cholesterol sulphate change)
− lateral heterogeneity in the plasma membrane:
o saturated lipids, cholesterol, GPI-anchored proteins, transmembrane proteins
(stabilizing the lipid bilayer), cortical actin → a meshwork of short actin polymers
making a grid under the PM, not stress fibers, a network for signalling proteins
o increased lipid packing and ordered
o decreased fluidity due to cholesterol
o asymmetrical distribution
o organization is not binary
29
,2. lipid rafts
− modulation of membrane organization
− varying raft coverage: isolated domains → percolating/continuous domains
− raft clustering & declustering:
o nanodomains → raft platforms
o due to signalling and trafficking or addition of clustering agents
o the amount is not increased locally but we have fusion
− lipid and protein interactions drive the lipid rafts architecture:
a) lipid-lipid:
cholesterol likes to
pack between the
tails and it makes
hydrogen bonds
b) lipid-protein:
hydrogen bonds
c) lapidated
proteins: proteins
with lipid tails
inserted into the
membrane where
they start
oligomerizing and
creating local architectures, serve as domain organizers
d) hydrophobic match/mismatch: α-helix must match the thickness of the lipid environment, a
mismatch is not favourable situation
e) transbilayer coupling: GPI-anchored protein interacts with actin through the long chain inner
leaflet lipids and lipid tails
− functions:
o concentrating signalling molecules
o allowing conformational changes
o immune signalling
o host-pathogen interactions
30
, 3. caveolae
− made of protein caveolin → 3
isoforms: caveolin 1, 2 & 3
− oligomeric cholesterol-binding
protein
− both the N and the C terminus face
the cytosol
− inserted in the inner leaflet of the
cells at the lipid raft
− hairpin conformation in the
membrane → allows molecule to
insert in the membrane
− domains:
o N-terminus
o conserved scaffolding
domain/CSD → cholesterol-
binding motif
o intramembrane domain
o C-terminus (3 lipid tails)
− caveolae = membrane invaginations
that can also fuse or pinching of the membrane → traditional, grape-like cluster, rosette, tubular
− many more components of caveolae other than caveolin
− caveolins interact with cavins (peripheral membrane proteins)
− caveolin oligomers + cavin trimers → curvature of the membrane
− very specific organization of the components
− functions: endocytosis, signalling, protection from mechanical stress
4. clathrin-coated pits
− made at the cell surface
− clathrin-dependent endocytosis
− 3 heavy + 3 light clathrin chains → 3x triskelion → clathrin
− the triskelion is held together by 3 tripod helices
− 30-40 triskelia assemble → pentagons or hexagons → cage around the invaginating membrane
− adaptins give specificity to one clathrin
− globular heads bind to adaptins which then directly bind to cargo
− AP2 adaptors → between the clathrin coat and the vesicle there are bulky heterotetrameric
AP2s. They bind clathrin on one hand and cargo proteins & membrane lipids on the other hand
→ bridging the vesicle cargo with the clathrin coat
− clathrin-coated pits detaching from the cell membrane: BAR proteins sense or induce the
curvature of the membrane & dynamin forms a ring around the neck of the vesicle until it
pinches of the membrane
− disassembly:
o for every clathrin triskelion removed from the vesicle coat, 1 auxilin molecule and 3
Hsc70 proteins are required
31
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper ninajunakovi. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €5,99. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 56326 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen