2.0 Protein Structures Flashcards
Levels and summary of protein structures?
Primary - sequence of amino acids held by peptide bonds
Secondary - Alpha helix or beta pleated - held by hydrogen bonds
Tertiary - arrangement of secondary structure into dimensions (compact structure)
Quaternary- 3D structure of multimer (multiple alpha/beta)
Post transcriptional modification (6)? And summary of each
Gamma Carboxylation of glutamate - e.g. in clotting factors (required vitamin K)
Adding carbohydrate (glycosilation) - adds solubility and protects from protolytic cleavage
Disulphite bond formation - e.g. in insulin and happens between two cystine residue - as they have SH
Phosphorylation - adding phosphate
Hydroxylation - e.g in collagen tissue (requires vitamin C)
Proteolytic cleavage - removing part of polypeptide e.g. in insulin
Why learn about protein structures?
Can help doctors tailor drugs to individuals
What reaction joins amino acids? Summarise it?
Condensation reaction between two amino acids - happened between N- and C- terminus. Leads to a peptide bond and a molecule of H20 is released.
What 5 forces hold proteins together and help stabilise them?
Covalent
Ionic
Van de Walls forces
Hydrogen
Hrydrophobic interaction
Describe covalent bonds in relation to protein?
Covalent - sharing electrons e.g. between amine and carboxyl group, can also happen in disulphide bridges in cystine
Describe hydrogen bonds in relation to protein?
Hydrogen - happens between atoms in different side chains, happens in the backbone, and happens between side chains and water molecules – stronger in the interior of protein
Describe ionic bonds in relation to protein?
Ionic - electrostatic attraction between oppositely charged side chains – stabiles alpha/beta (beta can be parallel or anti-parallel)
Describe VDWF in relation to protein?
Van de Walls forces - temporary weak electrostatic interactions – dipole in one atom causes one in another
If two electrons from adjacent atoms are close they repel
Size of electron cloud dictates distance required for VDWF
What do protein fold into (energy?)
conformation of lowest energy – can be spontaneous or involve ‘chaperones’
Describe hydrophobic interactions in relation to protein?
Outside only hydrophilic regions, inside only hydrophobic regions, causes movement of atoms to ensure this configuration – its a driving force for folding
What does misfolding of protein cause?
Pathological consequences e.g. Alzheimers
How do chaperones work?
They bind to partially folded peptides to ensure that the folding goes towards the energetically favoured way
Molecular animation?
Lysozyme - works on NAG, lactone is a competitive inhibitor of lysozyme (as similar structure to NAG)
Haemoglobin -
Chymotrpopsin - K(m) substrate concentration, V(max) velocity/rate – 5b is non-comp inhibitor as forms covalent bonds inhibiting aCT
