Coiled Coil Structures

Question 1

Describe the gross geometry of a coiled coil.

Answer 1

Each turn contributes 6.5 A of length.
Helices tilted 20 degress towards each other.
Diameter is 20 degrees.

Question 2

What is the pitch?

Answer 2

Superhelical repeat.
In a dimeric coiled coil = 140 A.
As number of helices increases so does length of pitch.

Question 3

How did the salt bridges become altered in GCN4pI when changed to tetramer?

Answer 3

Outside helical residues move closer together as structure gets larger.
G–>B and C–>E salt bridges.