Lecture 8: Protein Structure Flashcards
what do non-polar proteins bind to
lipids, eg in the membrane
what forms the shape of an alpha helix
hydrogen bonds forming between carbonyl groups and amine group 4 amino acids down the chain
how many amino acids are there per turn of an alpha helix
3.6
what is a beta pleated sheet made up of
laterally packed beta strands
what forms the shape of a beta pleated sheet
- hydrogen bonds between carbonyl groups and amine group of a neighbouring chain
what helps hold alpha chains and beta pleated sheets together
- turns, 3-5 amino acids long which form a sharp bend redirecting the polypeptide backbone
- loops, longer than a turn, tend to be hydrophobic and found on surface of protein
- random coils
what is the barrel configuration
- tertiary structure
- first and last strand form Hydrogen bonds, forming a barrel shape
what is the coiled coil configuration
- tertiary structure
- 2 or 3 alpha helices coil round each other
- hydrophobic amino acids line up together where the helices meet
- eg. keratin and collagen
- gives great structural strength
what is post translational modification
- covalent processing events
- addition of a modifying group
what can post translational modification change
- activity state
- localisation
- turnover
- interactions with other proteins
where are disulfide bridges found
- between SH and CH bonds, between two cysteines
- typically present in excreted proteins, as in the cytoplasm it’s a reducing environment which would reduce this bond
what can we use to predict the shape of a protein from its amino acid sequence
X-ray crystallography
what permanently dentaures proteins and what reversibly denatures them
- acid/base is reversible
- temperature is irreversible
what do molecular chaperones do
bind to a partially folded polypeptide and assist them in folding
what are the classes of chaperones
- heat shock proteins: more expressed at higher temperatures
- chaperonins: prevent protein aggregation, prevent non-productive intermediates and can shield proteins from its aqueous environment
