Zinc Proteins

Question 1

How many ligands does structural and catalytic zinc generally have?

Answer 1

S = 4
C = 3

Question 2

What is the structure of MT and why unusual?

Answer 2

Zn3S9 and Zn4S11 clusters

therefore 7 zincs and 20 cysteines. Normally every zinc bound by 4 sulphurs so would need 28 Cys

Question 3

Give three examples of regulatory roles for Zinc.

Answer 3

Interface sites - both tertiary and quaternary.
Insulin Hexamer - ZnN3 - important for insulin storage in Beta cells.
Zn Hook - Zn binding site brings two proteins together - 4 Cys –> strong interactions between two different types of proteins.

Question 4

How varied are the coordination dynamics of zinc?

Answer 4

VERY! Exchange rate:
CA = 3Y
Carbixypeptidase = 29 min
MT = 2s-1ms.

Question 5

What is the [] of zinc in the cell?

Answer 5

Total cellular Zn = 250 Um

Cell Zn = 250 pM.

Question 6

Give an example of zinc ordering quaternary structure of a protein?
What is the Zn hook?

Answer 6

Insulin hexamer
Each subunit contributes 1 histidine and important for storage of insulin in B cells.
ZnN3

Zn binding site bringing 2 proteins together. 4 cysteines so strong interaction between 2 proteins.