Lipidation

Question 1

How does lipidation affect protein function?

Answer 1

facilitating membrane association; dynamically regulating subcellular localization; stabilizing protein conformation and/or modulating activity

Question 2

what are the types of lipidation?

Answer 2

acylation– N-myristoylation, and S-palmitoylation

prenylation– farnesylation (15 Cs) or geranylgeranylation

Question 3

what is N-myristoylation?

Answer 3

irreversible addition of N-myristate to N-terminal Gly; promotes membrane association; N-myr. proteins are synthesized on free ribosomes–>n-myristoylation is usually co-translational

Question 4

consensus seq of N-myr

Answer 4

(M)GX’X’‘X’’‘(S/T)K
X’= small, uncharged (not Pro)
X’‘,X’’’= neutral>basic>acid (pro okay)

Question 5

what is the penultimate amino acid rule?

Answer 5

small amino acid, methionine will be gone

Question 6

NMT KO/inhibition?

Answer 6

prevents cyto membrane localization of N-myr proteins–> will be scattered throughout the cell

Question 7

how is the N-myr tail switched “off”?

Answer 7

phosphorylation of the S/T by PKC–>makes them negative; this causes them to repel from the negatively charged membrane–> myr. tail put away inside the protein

Question 8

S-palmitoylation is reversible

Answer 8

ya

Question 9

what is the purpose of S-palm?

Answer 9

promotes association with membranes; prevents protein aggregation

Question 10

what is prenylation?

Answer 10

irreversible addition of 15 or 20-Carbon donor (isoprenoid) via thioether bond; isoprenoids attach to C-terminal cys; catalyzed in cytosol;

Question 11

consensus seq of prenylation?

Answer 11

CaaX, where a = aliphatic (no ring side chain)

Question 12

what is X in the consensus sequence for FTase?

Answer 12

X- Ala, Gln, Ser, Met, Phe

Question 13

what is X in the con seq for GGTase-1?

Answer 13

X= Leu, Phe, sometimes Met

Question 14

what does prenylating a protein do?

Answer 14

localization of signalling G-proteins at the plasma membrane, facing the cytosol

Question 15

what does RCE1 do?

Answer 15

cleaves the AAX from the protein and replaces it with O;

Question 16

what does IMCT do?

Answer 16

with SAM, it methylates the C-terminus–>becomes an ester bond, neutral, associates with membranes

Question 17

compare and contrast S-palm and N-myr association

Answer 17

S-palm reversible, N-irreversible; both used to localize protein to membranes; no consensus seq for S while N’s is MGX’X’‘X’'’S/TK; S is usually post-trans while N-is co trans;