Protein structure and protein folding disease

Question 1

What is meant by primary protein structure?

Answer 1

• bonding of amino acids to from peptide bonds

- amino acid has amino group, alpha carbon, carboxyl group, R-group

Question 2

Name the different types of secondary protein structure that exist:

Answer 2

• Secondary protein structure refers to the regular structure
• Alpha helix- refers to H-bonding between amide nitrogens and carbonyl carbons
• B-pleated sheets, anti-parallel where polypeptide runs in opposite directions, parallel where they run in the same directions
• B-hairpin turns- abruptly changes its direction

Question 3

What is meant by tertiary structure?

Answer 3

• irregular folding of the protein (disulphide bridges)

Question 4

What is meant by quartenary structure?

Answer 4

• seperate folded subunits begin to form oligomeric proteins

Question 5

Where is a protein folded and what forces control this structure

Answer 5

• either folded into the cytoplasm or undergoes the secretory pathway
• chaperons assist in proper protein folding

Question 6

What factors can cause a protein to mis-fold?

Answer 6

DNA mutation, mutations that causes production of a protein that is destabilised, stresses during the lifetime of the protein, environmental factors and post transitional modifications

Question 7

Explain how protein folding can lead to reduction of absence of normal protein using cancer to illustrate the answer:

Answer 7

• Normal p53- supresses abnormal cell proliferation and is involved in programmed cell death
• p53 looses its ability to block abnormal cell death then it is unable to carry out apoptosis and hence the cancer is able to proliferate and is more likely to be fatal for the host

Question 8

Explain how accumulation of mis-folded proteins leads to mad cow disease:

Answer 8

• Abnormal variants of naturally occurring PrPc
• Prions make other proteins misfold which leads to a domino effect meaning over time this will make plauqes which will destroy the brain cells

Question 9

How are misfolded proteins able to be treated?:

Answer 9

• Inhibition of protein aggregation
• Chemical chaperones
• Non-homolegous (healthy) prion proteins- these often come from another species