lipids to membranes

Question 1

How can lipids move in membranes?

Answer 1

laterally:
- the movement of a lipid within a single membrane leaflet

Transversely:

• movement from one lipid to another
• catalysed by flippases
• causes asymmetry of lipids between leaflets

Question 2

What are the tree types of membrane protein?

Answer 2

Integral membrane ptomaines:

• α-helices that can form bundles
• β-sheets that can form barrels

Peripheral membrane proteins:

• only interact with head group of lipid
• or integral proteins

Membrane anchored proteins:

• lipid tails integrated into membrane
• Either cytoplasmic (S-acylation, N-myristoylation, Prenylation) OR extracellular (Lipoprotein, GPI anchor)

Question 3

What are properties of S-acylation?

Answer 3

• cytoplasmic
• PTM
• reversible
• on cysteine residue sulphur via thioester bond

Question 4

What are properties of N-myristolyation?

Answer 4

• cytoplasmic
• PTM/coTM
• Irreversible
• occurs on N-terminus if glycine via amide bond

Question 5

What are properties of Prenylation?

Answer 5

• cytoplasmic
• PTM
• Irreversible
• c-terminus on cystine that is part of a CaaX motif

lipid added depends on X

Question 6

What are properties of Lipoproteins

Answer 6

• in prokaryotes
• extracellular
• PTM
• on N-terminus if cystine via thioester bond.
• also an amide bond with aa of cystine
• three tails

Question 7

What are properties of GPI anchors

Answer 7

• in eukaryotes
• extracellular
• coTM
• On C-terminus
• several sugars before the last sugar inositol.
• On inositol one lipid tail is bonded via an ester bond
• two lipid tiail are bonded to phosphoglycerol (bonded to the inositol)

GPI = Glycosyl-phosphatidyl-Inositol