Biol 115- Protein Biochemistry Flashcards
(19 cards)
what is serum albumin?
the major protein (40g/L) present in blood plasma (total protein content 70 g/L)
describe 2 main functions of human serum albumin
- as a transporter of smaller, mostly hydrophobic molecules.
- as the major contributor (80%) of the osmotic swelling pressure of blood plasma
not the same as like ovalbumin in eggs and stuff.
why are things given the names serum + plasma? how do they link to clotting?
serum because you can allow the blood to clot + after centrifugation, you’re left with serum.
Plasma is when you add like a coagulate or something, so it doesn’t clot.
this graph (done after classical electrophoresis) shows the distribution of proteins in the blood + albumin makes up the highest peak on the graph.
which electrode (positive or negative) does albumin migrate to?
the positive electrode
this graph (done after classical electrophoresis) shows the distribution of proteins in the blood + albumin makes up the highest peak on the graph.
however, lots of other molecules also migrate to the same place, despite the fact they’re quite different from albumin.
what is an explanation for this?
they could bind to the albumin, as they migrate with it
this is a forest plot, often used in a meta-analysis (lots of categories e.g. different age groups) of the effect of perhaps a drug or treatment. what do meta-analyses entail?
meta-analyses take lots of studies which have examined the same thing, and shows the outcome of each, and of them all added together
what is hypoalbumenia (causes + symptoms)?
low levels of albumin in the blood.
caused by liver + kidney disease, and malnutrition (decreased protein intake)
symptoms: fatigue, weakness
this graph shows the administration of albumin in different doses to combat different diseases xxx
this shows the structure of albumin. despite its common occurrence in proteins, the isolated alpha-helix is only marginally stable in solution.
how does this affect the way the alpha-helices are packed + how does this help with function?
they tend to be packed pairwise in proteins with their hydrophobic residues pointing towards the molecule’s core (hydrophobic core for transport).
Also increases stability of the helix.
what is the Mr and pI (isoelectric point, kind of like pKa) of HSA (human serum albumin)?
Mr = 66,500
pI = 5.67
HSA consists of a single polypeptide chain, containing how many amino acids, with how many intra-chain disulphide bonds?
585 amino acids, with 17 intra-chain disulphide bonds
These disulfide bonds pull the molecule into a series of large (L) and small (S) double loops.
there are 3 similar domains in HSA, and what does further examination show?
examination of the amino acid sequence shows that there are repetitions even from one individual loop to another.
this shows the secondary structure of HSA. what does this confirm about alpha helices content?
most of it is alpha-helices (approx 67%)
everything in green is generating alpha helices.
how do we reckon that the recurring LSL-LSL-LSL loop of HSA evolved from just one L (original gene). give the presumed sequence.
L- DNA coding for L loop
S- DNA coding for S loop
the AA sequence of albumin has an unusually high percentage of Cys (35 out of 585 amino acids).
the primary structure also contains a single free sulfhydryl (Cys-34), shown here in reduced form.
in circulating plasma, how much of free sulfhydryl Cys-34 is oxidised?
30%
albumins can bind to each other from the cysteine ends, which is cool.
albumin contains multiple binding sites, notably for long-chain fatty acids (free fatty acid transport), for small heterocyclic or aromatic carboxylic acids + for metals.
Cys-34 (SH-group) can bind ions of Cd, Au, Hg, Ag. what does N-terminal His-3 bind with? (2)
Cu (II), Ni (II)
In fact, Cu(II) transport in the blood is primarily as a complex with albumin.
a number of hormones + drugs are transported by albumin. these include… (4)
aspirin, AZT, penicillin + warfarin
why is the transport of drugs by albumin pharmacologically important?
drugs compete for binding sites + small molecules, not transported on proteins, may be excreted by the kidney into the urine.
