lecture 26 - intrinsically disordered globular proteins

Question 1

question: what sort of aa composition would you expect in a protein that does not fold up?

a) rich in gly and ala
b) lots of hydrophobic and few hydrophilic
c) lots of hydrophilic and few hydrophobic
d) lots of large side chains
e) a and c
f) b and d

Answer 1

answer: e)

Question 2

explain the primary structure of intrinsically disordered proteins

Answer 2

• rich in charged, polar uncharged, gly and/or pro (not in the G-X-Y pattern) amino acids
• lack of hydrophobics = no opportunity to form a hydrophobic core
• gly and/or pro = secondary structure formation is not favoured
• hydrophilic residues tend to remain in contact w solvent = no folding into 3D structure

Question 3

explain the functions of intrinsically disordered proteins (3) and give an example of one

Answer 3

• flexible nature = allows for adaptibility and functional promiscuity
• has roles in regulation of transcription and translation
• has roles in other regulated processes
• e.g. calpastatin = a calpain inhibitor (protease) that has no secondary or tertiary structure except when bound to caplain - then has 3 alpha helices

Question 4

how are intrinsically disordered proteins regualted? give examples (2)

Answer 4

often through post-translational modifications:

1) phosphorylation of ser, tyr and tyr (neutral to 2 neg
(2) acetylation of lys (1 pos to neutral)

Question 5

what effect does the regualtion of IDPs have on them?

Answer 5

-post translational modifications can change the ability of an IDP to bind to its partner(s)
(many IDPs adopt a secondary structure upon binding to their target - “ligand-induced conformational change”)

Question 6

do globular proteins also undergo reversible post-translational modifications?

Answer 6

yea