Lecture 1 Flashcards
(26 cards)
Define 3 major classes of globular protein.
α-domain structures made up entirely of α-helices.
β-domain helices made up entirely of β-strands.
αβ-domain structures made up pf mixed α-helices and β-strands. Generally more complex in structure.
As an isolated α-helix is barely stable in solution, how are they typically arranged?
Pairwise in proteins, with hydrophobic residues pointing towards the core.
What is the major protein present in blood plasma, and in what concentration?
Serum albumin (40g/L).
What is the total concentration of protein in blood?
70g/L.
2 functions of serum albumin?
Transporter of smaller (typically hydrophobic) molecules. Major contributor (80%) of osmotic swelling pressure of blood plasma.
To which electrode does albumin migrate to?
Positive electrode.
To which electrode does albumin migrate to?
Positive electrode.
What is the pI (Isoelectric point)?
The pH at which a particular molecule carries no net overall charge.
What is the Mr and pI of HSA (Human Serum Albumin)?
66,500 Da, 5.67.
How would you define HSA’s structure?
Almost entirely α-helical.
How many polypeptide chains,
amino acids,
and intra-chain disulphide bonds are there in HSA?
1,
585,
17.
What is the purpose of disulphide bonds in HSA?
To form large (L) and small (S) double loops.
How may HSA have evolved?
L (large loop) gene duplicated twice, forming LLL. The middle gene mutates, creating LSL. The sequence then duplicates twice, forming LSL LSL LSL.
What amino acid does the amino acid sequence of albumin contain a very high percentage of (and how many)?
Cysteine. (35/585).
Of note, what does the primary structure of cysteine contain?
One free sulphydryl.
Of note, what does the primary structure of Cys-34 contain?
One free sulphydryl.
What percentage of free sulphydryl Cys-34 is oxidised?
30%.
Some preparations of serum albumin can contain up to ??% albumin dimers.
Also, what must happen to form an albumin dimer?
20%.
Cys-34s must disulphide bond to each other.
Albumin’s many binding sites can carry which 3 types of molecule?
Long-chain fatty acids,
Small heterocyclic/aromatic carboxylic acids,
Metals.
What 4 ions can Cys-34 bind to?
Cd, Au, Hg, Ag.
His-3 on the N terminal of HSa can bind which ions?
Cu(II), Ni(II).
How is Cu(II) typically transported in the blood?
Complex with Albumin and free His.
What 4 drugs can be transported via Albumin?
Aspirin, AZT, Penicillin, Warfarin.
What may happen to small molecules not transported in the blood via protein?
Excretion via the kidney into the urine.
