Lecture 7. Proteins Flashcards
What does a peptide bond do ?
Connects amino acids
What direction are hydrogen bonds ?
Diagonal
Do outward facing side chains play a part in hydrogen bonding ?
No
What is dihydrofolate reductase ?
An enzyme that reduces dihydrofolate to tetrahydrofolate
What is the coenzyme of dihydrofolate reductase ?
NADPH
What does dihydrofolate reductase do ?
Important in one carbon metabolism and synthesis of nucleic acid
What are super helixes ?
Two right handed alpha helix intertwined with the presence of a disulphide bridge
What is collagen the main component of ?
Skin, bone, tendon, cartilage and teeth
What is the structure of collagen ?
- Rod shaped
- 3000 A long, 15 A diameter
- Three left-handed helical 1000 residue polypeptide chains
What is the third amino acid in collagen
Glycine
What is the frequent repeat seen in collagen ?
Glycine, proline and 4-hydroxyproline
Discuss a quality control measure taken if a protein is still in the cell
Protosomes and other molecules can degrade the protein into amino acids and try again
What happens if a protein is folded incorrectly outside the cell ?
It may still function or it may aggregate to amyloid fibrils
What is alzheimers caused by ?
The amyloid fibrils in brain kills cells
What is parkinsons caused by ?
Aggregation of alpha synuclein
What is needed for a protein to unfold ?
- Ribonuclease A to unfold
- Addition of a chemical denaturant
- Reducing agent added to break disulphide bridges
What contains all the information for the protein to fold ?
The amino acid polypeptide chain
Do we observe step wise, gradual folding en-route to the native state ?
No we see hydrophobic collapse and slow reorganisation of side chains to attain native structure
Thermodynamically, what is the native structure at ?
Global free energy minimum
What do molecular chaperones or chaperonins do ?
Assist protein folding
What is an assay ?
A track protein
What must be used to purify proteins ?
an assay
What is isoelectric focusing ?
Protein separation based on pI
