4 Flashcards
how is hemogolbin described
tetramer or dimer of alpha-beta protomers
what feature makes a structure an oligomer
repeating units
what is the repeating unit in an oligomer
protomer
what are oligomers associated with
a symmetry form
how are errors in translations affected by the quaternary structure
less critical
what is pseudosymmetry
non-identical homologous subunits are related by symmetry
what are the types of symmetry
Cyclic, dihdedral, tetrahedral, octahederal, isocaheadral
describe the axes in Dn
2N protomers arranged around 2 axes
one N fold and one 2 fold
what is helical symmetry
protomers related by rotation and translation
what are the fold axes in tetrahedral symmetry
3 fold and 2 fold
what are the fold axes in octahedreal symmetry
2, 3, 4
what are the fold axes in icosahedral
2, 3, 5
what are the types of forces in protein folding
weak, non covalent
what can destroy the native state of a protein (4)
heat pH detergents organic solvents
what are the two denaturants of interest
guanidinium and urea
descibe the effects of the two denaturants of interest
chaotropic, water soluble, disrupt H-bonding
what are the two reducing agents of interest
beta-mercaptoethanol and DTT (dithiothreitol)
what kind of process is denaturation
cooperative
what is the midpoint of transition for denaturant characteristic of
protein and denaturant
what effect does unfolding part of the protein have on the energy required to unfold the rest of the structure
decreases
what is the state between secondary and tertiary structure
molten globule
what is misfolding
stable structure but not native
what are the disease states leading to misfolding
amyloidosis - huntington’s / alzeimers
prion disease - BSE, scrapie
collagen defects - osteogenesis imperfecta
what 2 things can assist with folding
chaperones or isomerases
what are the 2 types of molecular chaperones
chaperonins and Hsp
what sre the two types of isomerases
protein disulphide isomerase
peptide prolyl isomerase
how do chaperones work
isolate misfolded proteins so they do not interadr
what do chaperones use to carry out their activity and why
energy (ATP hydrolysis) to unfold the protein substrate
is chaperone activity kinetic or thermodynamic
kinetic
what are the two bacterial chaperones of interest
DnaK Hsp70 and DnaJ Hsp40
what is responsible for the nucleotide exchange associated with protein assisted folding
GrpE
what does ATP hydrolysis do for assisted folding
changes binding site for protein substrate
describe Hsp 70 and Hsp 40 actions
DnaK binds with ATP then associates with DnaJ and midfolded substrate
what is the GroEL/GroES complex (chaperonin)
- GroES cap binds to GroEL ring
- unfolding of misfolded protein with ATP hydrolysis (7 ATP)
- another misfolded substrate enters with 7 ATP
- release of GroES cap, ADP and protein
what are the two properties of PDI
isomerase or oxidoreducatase
