Week 6 Bollough Lecture 14

Question 1

When is the KcsA channel open?

Answer 1

At low pH

Question 2

What is KvaP?

Answer 2

A voltage gated K+ channel

Question 3

What is the structural difference between KcsA and KvaP?

Answer 3

There are 4 extra helices used to detect voltage

Question 4

What is the structure of KvaP?

Answer 4

Has 6 transmembrane helices in total;

a) S5 and S6 are analogues of the outer and inner helices in KcsA.
b) The S1 to S4 form the membrane embedded voltage sensor
c) There is a linker sequence which links S4 (voltage sensor) and S5 (pore domain)
i) There is also a paddle between S3 and S4 which when moved, it moves the linker to trigger the opening or closing of the pore domain

Question 5

How does the voltage sensor work in KvaP?

Answer 5

R1 to R4 form the ‘gating charges’ in an otherwise predominantly hydrophobic

a) region 4 arginines which make up the gating charges positively charged
b) sense the voltage
c) positives will move away or towards different charges
d) When membrane voltage is changed there is a transient movement of the gating charges within the membrane

Question 6

Explain the opening and closing of the KvaP?

Answer 6

Only has 2 configurations;

a) Open
b) Closed
i) The percentage of how many times it is open or closed depends on tehe voltage; more positive voltage more open.