Proteins 4 Flashcards
what type of covalent bond help stabilises a proteins tertiary structure?
Disulphide bonds between cysteine residues (formed by reversible oxidation)
what type of non-covalent bonds help stabilise the structure of proteins?
- hydrogen bonds
- hydrophobic effects
- ionic bonds
- Van der Waals interactions (quaternary)
hydrogen bond
charged amino acid chains interact with water and salt when the protein is unfolded
ionic bonds
between carboxylated ion of an acidic residue and an ammonium ion of a basic residue
hydrophobic interaction
requires thermodynamic driving forve for association of hydrophobic groups in aq solution
what are free cysteine
cysteine residues not involved in disulphide bonds
how to break a disulphide bond
add a reducing agent
how to remake a disulphide bond
add an oxidising agent, such as H2O2
define native protein
proteins in any of their functional, folded conformations
define denaturation
a loss of 3D structure sufficient to cause loss of function
define renaturation
the regaining of a denatured proteins native structure and biological activity
how are post-translational modifications useful?
- increases array of functions that proteins can perform
- can increase stability of a protein (acetyl groups added to amino termini of proteins can help them resist degradation)
- can alter biochemical activity (phosphorylation for activating or inhibiting a protein –> regulate cellular processes)
- can allow proteins to act as markers by the addition of special groups
- can aid protein signalling by allowing proteins to participate in more interactions with other proteins (the addition of sugars)
define proteostasis
the dynamic regulation of a balanced, functional proteome
pathways that contribute to proteostasis
- misfolded proteins can be remodelled by chaperones
- misfolded proteins can be degraded by ubiquitine proteasome system
what can be used to denature proteins?
- heat
- extreme pHs
- organic solvents
- solutes
- detergents
