EXAM1 Fall06 11 am key - EXAM I KEY BIOCHEMISTRY 460 11:00...

EXAM I - KEY
(September 20, 2006)
BIOCHEMISTRY 460
11:00 am section
Using 2D gel electrophoresis Professor DoGood has identified a protein involved in
premature cell death (PCD) in individuals with chronic illness. She finds PCD is a heme protein
which can bind nitric oxide (NO), and when NO is bound, PCD is a protease which cleaves
peptide bonds on the C-terminal side of Asp and Glu. This proteolytic cleavage results in cell
destruction.
1. Briefly describe what information about PCD can be obtained from the following techniques
(5 points each).
a. Iso-electric focusing.
Isoelectric point, that is, the pH at which the net protein charge is zero
b. Gel filtration.
Molecular weight
2. Dr. DoGood determines a number of properties of PCD. For each of the observations given
below, briefly answer the question (5 points each).
a. PDC is found to bind to carboxy methyl cellulose when chromatographed at pH 7.
What does this tell Dr. DoGood about the protein charge at pH 7.
That it is positive
b. PDC is found to be rich in the amino acid Ser. Where in the tertiary structure would
Dr. Dogood expect to find the Ser, and why?
On the surface of the protein since the side chain is polar
3. Dr. DoGood determines a molecular weight of 57 kD for PCD. Following treatment with
mercaptoethanol, two bands are found on gel electrophoresis with apparent molecular weights of
32 kD and 25 kD. What does this suggest about the quaternary structure and covalent