2. The EF and Calmodulin

Question 1

what is KD

Answer 1

a measure of the affinity between two molecules, usually a receptor and ligand

Question 2

what are the units for KD

Answer 2

molar (M)

Question 3

what happens if:

• the KD is low
• the KD is high

Answer 3

low= affinity of ligand for receptor is very high
high= the affinity of the ligand for the receptor is very low

Question 4

what is equilibrium

Answer 4

a state of balance due to the equal action of opposing forces

Question 5

what is Le Chateliers principle

Answer 5

we can force a change in equilibrium by changing concentration of either A or B

Question 6

what is the EF hand

Answer 6

a protein motif associated with calcium binding

Question 7

what is a motif

Answer 7

a conserved amino cid sequence

Question 8

what characterises the EF hand

Answer 8

a helix-loop-helix configuration

Question 9

what is the KD of an EF hand

Answer 9

~ 10^-6 M

Question 10

how does EF hand bind to calcium

Answer 10

acidic amino acid residues have carboxylate oxygen ligands- these act as ligands for metal ions such as calcium

Question 11

how many residues in a EF hand

Answer 11

29 residues

Question 12

which residue permits a sharp bend in the loop

Answer 12

Gly at position 15

Question 13

what does calmodulin stand for

Answer 13

calcium modulated protein

Question 14

how many EF hands in calmodulin

Answer 14

4

Question 15

what occurs in calmodulin when calcium binds

Answer 15

change in shape, it is now able to bind and activate kinases

Question 16

name 2 functions of calcium

Answer 16

• secondary messenger in muscle contraction

- controls release of hormones and neurotransmitters

Question 17

describe the structure of calmodulin

Answer 17

• dumb-bell shape

- N- and C- terminal domains each have 2 EF hands separated by a 6-turn alpha helices

Question 18

true or false:

calmodulin’s occur in 4s

Answer 18

false: occur in pairs

Question 19

what happens when one EF hand binds calcium

Answer 19

becomes easier for the other EF hand in the same domain to bind a calcium

= COOPERATIVE CALCIUM BINDING

Question 20

what is an apo structure

Answer 20

one that is missing its ligand or binding partner

Question 21

how is the structure of apo calmodulin different to calmodulin

Answer 21

• flexible and dynamic molecule

- region between N and C terminal is folded and packed together

Question 22

what happens when 4 calcium molecules bind on calmodulin

Answer 22

a conformational change occurs, exposing a hydrophobic patch, this allows interaction with other proteins

Question 23

what is the function of the hydrophobic patch

Answer 23

when exposed allows interaction with other proteins

Question 24

give examples of target molecules for calmodulin

Answer 24

phosphorylase kinase
adenylate cyclase
ca2+ATPase