Oligopeptides
large number of amino acids, synthetic residues
Polypeptide
natural long chain of aa
Protein
large polypeptide with biological function
Primary Structure
- covalently bound amino acid sequence
- rigid/planar
- 3D structure determines function
Folding conformations are limited….
to minimize steric conflicts
Secondary Structure
- polypeptide backbone
- a-helix, B-sheet
a-helix
H-bonds between backbone in the same helices
B-sheets
H-bonds between neighbouring strands
____ secondary structure linked by ____
regular, irregular
Tertiary
All atoms in a polypeptide
- amino acid chains
- prosthetic groups
- arrangement of secondary structures
Fibrous
- insoluble
- long filaments
- structural or connective
Globular
- soluble
- non-polar core (hydrophobic side chains)
- polar surface (hydrophilic side chains)
Regular found in ____ and ____ found outside
interior, irregular
soluble globular protein’s driving force….
hydrophobic effect
Salt bridges
- electrostatic interactions between - and +
- fine tune and stabilize 2 and 3 structures
Disulphide bonds
covalent bonds between cysteines
- stabiling crosslinks for extracellular proteins
- do not form in reducing environment
Domain
polypeptide segment in single unit with hydrophobic core
Motif
short region of polypeptide with recognizable 3D shape (like prosthetic groups)
Prosthetic group
non-peptide component that permanently incorporated in a protein
-structure and function chemical groups
Globular proteins stabilized by ….
weak non covalent forces = easily unfolded/denatured
what disrupts disulphide bridges
reducing agents DTT, requires chemical reaction
Quaternary Structure
more than one polypeptide chain, each one called subunit (2 = dimer etc)
Quaternary structure stabilized by….
hydrophobic interactions and H-bonds
