L6- tertiary and quaternary structures Flashcards Preview

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Flashcards in L6- tertiary and quaternary structures Deck (15):
1

What do loops and turns do?

Connect alpha helices and Beta strands and allow a peptide chain to fold back on itself to make a compact structure

2

What are loops?

Connections which often contain hydrophilic residues and are found on protein surfaces

3

What are turns?

Loops containing 5 residues or less

4

What are tertiary structures primarily stabilised by?

Non-covalent interactions between side chains

5

What, apart from non covalent interactions between side chains, stabilises tertiary structures?

disulfide bridges

6

How many amino acids in each alpha helix turn?

3.6

7

What are supersecondary structures/ motifs?

Recurring folding patterns comprising at least 2 connected secondary structure elements

8

What are the 8 motifs?

  1. Helix-loop-helix (2 helices connected by turn)
  2. Coiled-coil (2 helices that interact in parallel through their hydrophobic edges)
  3. Helix bindle (several alpha helices that associate antiparallel manner to form bundles)
  4. B-alpha-B unit (2 parallel B strands linked to alpha helix by 2 loops)
  5. Hairpin (2 anitparralel B strands connected be a B turn)
  6. B meander (antiparallel sheet made of B strands connected by loops or turns)
  7. Greek key (4 antiparallel strands - 1,2 in middle, 3,4 on outside)
  8. B sandwich (stacked B strands or sheets)

9

What are domains?

  • Independently folded compact units in proteins
  • 25 to 300 amino acid residues
  • Domains can be connected by loops and associated together by non-covalent interactions between side chains

10

What do domains do?

Domains usually have a stand alone function. Can combine domains for multi-function protein.

11

What can domains show us?

Can show evolutionary conservation of protein structure. A domain fold can be conserved in many proteins shen the primary structur is undetectable different.

12

What are the 4 common domain folds?

  1. Parallel twisted sheet
  2. B-barrel
  3. alpha/beta barrel
  4. B helix

13

What do folding patterns allow us to do?

Classify protein structure into 4 categoriees with common domains and motifs

14

What are the 4 categories of protein structure?

  1. All alpha
  2. All beta
  3. Mixed alpha/beta (alternating alpha and beta bits)
  4. Alpha and beta (cluster of alpha then beta seperate)

15

What are quaternary structures?

Organization of subunits. Subunits have defined stoichiometry and arrangement.