L1-3 quiz

• in alpha-domain structures:

  • alpha-helices tend to occur in pairs
  • alpha-helices are the only significant secondary structures
  • large hydrophobic residues point towards the molecule's core
• serum albumin:

  • occurs as an extracellular protein in blood
  • binds and transports free fatty acids
• serum albumin:

  • has Mr of 66000 and an acidic pl
  • has a 3-domian structure
  • has a combination of large and small double loops
• cysteines in serum albumin:

  • represent 35 out of the 585 amino acids
  • may, if they retain a free -SH group, bind monovalent ions of Ag and Au
• free [Ca2+] is:

  • 10^-3 M in the extracellular environment
  • increases within cells upon stimulation
• EF hand contains:

  • amphipathic E and F alpha-helices
  • residues that provide oxygen ligand for calcium ions
  • conserved loop region hydrophobic region (isoleucine)
  • 29 amino acids
• calmodulin:

  • adopts a dumb bell shape
  • contains a linking six-turn alpha-helix in the centre of the molecule in the calcium bound form only
  • can fold at a critical Ser residue in the centre of the molecule
  • is a sensor of intracellular calcium ion concentration
• function of myoglobin in:

  • humans is to facilitate diffusion of oxygen to mitochondria
  • diving mammals is to store oxygen in the muscle cells
• the iron in the haem group in myoglobin:

  • is in the Fe II state
  • is bonded to 4 N atoms in protoporphyrin IX
  • is directly bonded to the proximal His
• myoglobin:

  • is an intracellular protein of Mr 17000
  • contains right-handed alpha-helices