Membrane Proteins

Question 1

What are the for major forces maintaining the structure of membrane proteins?

Answer 1

Pressure exerted by membrane

Interactions with specific lipids

Individual interactions of AAs

Shielding of polar AAs

Question 2

How can the KcsA be studied using monoclonal Abs?

Answer 2

Raise them against hydrophilic portion of molecule

Solubilised KcsA mixed with Abs and CRYSTALLISES via pp interaction created by Abs

! Micelles still used and interactions with abs distort native structure.

Question 3

What two methods are used to determine the structure of B2 adrenergic?

Answer 3

Co crystallisation with neutral antagonist Carazolol

WITH Antibody (Fab)

OR reengineering one loop using T4 lysozyme.

Question 4

What are the main differences between rhodopsin (bovine) and B2 adrenergic?

Answer 4

Loops

B2-AR must rigidify to keep access free to ligand binding site

Rhodopsin doesn’t have to as ligand is light.

Question 5

Why is 2D membrane array imaging not sufficient for Br?

Answer 5

Good resolution in membrane plane

Poor in Z dimension (7A).

Question 6

How canoe achieve a 3D image of Br?

Answer 6

Series of 2D images

Tilt each image by a specific angle

Improve resolution by tilting along different axes.

3.2A in XY and 3.6 in Z!

Question 7

What are the key features of K channels?

Answer 7

Tetramers with core helices formed

2 proper helices form channel and half helix for specificity

10e8 conduction rate

Question 8

What alternative method can be used to determine the structure of BR?

Answer 8

Create lipid vesicles with bR and F1F0

Sample illuminated and proton pumping begins.

Question 9

What is the resolution of bR via X Ray?

Answer 9

1.4 A

7 helices, short AP beta strand and retinal inside.