L6- tertiary and quaternary structures Flashcards Preview

Biochemistry > L6- tertiary and quaternary structures > Flashcards

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

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


What are loops?

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


What are turns?

Loops containing 5 residues or less


What are tertiary structures primarily stabilised by?

Non-covalent interactions between side chains


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

disulfide bridges


How many amino acids in each alpha helix turn?



What are supersecondary structures/ motifs?

Recurring folding patterns comprising at least 2 connected secondary structure elements


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)


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


What do domains do?

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


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.


What are the 4 common domain folds?

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


What do folding patterns allow us to do?

Classify protein structure into 4 categoriees with common domains and motifs


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)


What are quaternary structures?

Organization of subunits. Subunits have defined stoichiometry and arrangement.