Membranes And Membrane Proteins Questions (Papers I and IV)

1995

Paper I

"On the basis of what information are membrane proteins frequently
classified as integral or peripheral?  A membrane protein has three
subunits: a, b, and g, and can be reconstituted as an active protein in a
bilayer.  Explain how you would use the primary sequences (obtained from
the gene sequences) and other information about each subunit to formulate
a model for the structural organisation of the protein with respect to the
membrane.  Explain what pitfalls and problems might beset such an
exercise.  How might you test whether the protein undergoes a
conformational change during its functional/reaction cycle?"

Paper IV

"To what extent do we understand how the binding of ligands to receptors
results in movement of ions across membranes?"

1996

Paper I

"How have studies of integral membrane proteins resolved to less than 10Å
helped in our understanding of their function?  Discuss with examples."

Paper IV

"Describe the methods used to identify specific proteins which interact
with the intracellular domain of the PDGF receptor, and to determine the
consequences of these interactions."

"Discuss the mechanisms used by epithelial cells to maintain distinct
domains of the plasma membrane."

1997

Paper I

"What methods, other than X-ray crystallography, are available to probe
the structure of membrane proteins?"

Paper IV

"To what extent can the physiological properties of either then nicotinic
acetylcholine receptor or voltage gated K+ channels be explained in terms
of molecular structure?"
1998

Paper I

"The crystal structure of bacteriorhodopsin has recently been solved by
X-ray diffraction methods at 2.5Å and refined to a crystallographic R
value of 22.1%.  Use your knowledge of bacteriorhodopsin and protein
crystallography to answer the following:

(a)	Describe the structure as represented in fig. 1.  How does the X-ray
	crystal structure compare with the structure obtained from recent
	high-resolution EM with 2D crystals?
(b)	Fig. 2 shows a schematic representation of groups that may be involved
	in the light-driven hydrogen ion transport.  Comment on the arrangement
	for hydrogen ion transport and describe, where appropriate, other evidence
	in support of the roles of some of the individual amino acids.
(c)	Indicate briefly the problems involved in membrane protein
	crystallisation.
(d)	The crystals of bacteriorhodopsin used for the X-ray studies had
	dimensions approximately 30 x 30 x 5mm.  Briefly, what advances in X-ray
	methods have made data collection from such small crystals possible?

Paper IV

None.

1999

Paper I

" 'Determination of the structure of membrane proteins is no longer an
insurmountable challenge.'  Discuss, with specific examples, how recent
high-resolution EM and X-ray diffraction studies support this statement."

Paper IV

"Describe the methods available for predicting the topology of an integral
membrane protein composed of a single polypeptide chain.  Discuss the
experimental procedures that might be used to validate such a topological
model."

"How do ion channels discriminate between various ions?"

2000

Paper I

"Discuss whether non-crystallographic methods are of continued relevance
to the study of the structure of integral membrane proteins."

Paper IV

"Why are studies of cell membranes of biomedical importance?  Illustrate
your answer by reference to specific examples."