Protein Structure
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The misfolding of what protein causes Alzheimers?
Amyloid B-peptide or Tau in the ER
The misfolding of which protein causes Parkinsons?
a-synuclein in the cytosol
The misfolding of which protein causes Cancer?
p53 in the cytosol
How many different amino acids are there?
20
What are the two major protein structures?
Alpha helix Beta sheet
How can the alpha helix be represented?
Backbone Sticks Ribbons Space filling
Where was the alpha helix first seen?
In the protein alpha keratin
Where do hydrogen bonds form in an alpha helix?
Between every forth peptide bond So on C=O is linked to a N-H
How often do alpha helixes have a complementary turn?
Every 3.6 amino acids
Where are alpha helixes abundant in the cell?
Cell membranes ie in transport proteins or receptors
Which amino acids do not favour helix forming?
Proline and Glycine
Beta Sheets can run in what two directions?
Parallel or anti-parallel
Which amino acids are usually found in the middle of the B sheets and why?
Aromatic residiues - Tyr, Phe, Trp, Val and Ile They are hydrophobic
What is always at the start of a protein?
The N terminus - NH2 COOH is always at the end
What are the four subunits of Src tyrosine kinase?
SH3 domain SH4 domain Small kinase domain Large kinase domain
In general, more complex organisms’ proteins have more what?
They have additional domains
What are the 3 types of non covalent weak bonds that can hold proteins together?
Hydrogen bonds Electrostatic attraction Van der Waals Attractions
Where do disulphide bonds form?
Inbetween two adjacent cysteine residues
Where do polar side chains tend to form in a folded protein?
On the outside of the folded protein so they can interact with water
The core of a folded protein can be known as what?
Hydrophobic
How can primary sequence be determined?
Inferred from DNA sequence Determined directly by amino acid sequencing using Edman degredation (chemical degredation) Mass Spectrometry (physical degredation)
What chemical does edman degredation use?
Phenylisothyocyanate (PITC)
Adding PITC to an amino acid chain forms what?
Phenylthiocarbamoyl derivative with the N terminus
What is formed when the N terminus is cleaved?
Cyclic compound of phenylthiohydantoin forms PTH amino acid This does not change the amino acid