2. The EF and Calmodulin Flashcards
what is KD
a measure of the affinity between two molecules, usually a receptor and ligand
what are the units for KD
molar (M)
what happens if:
- the KD is low
- the KD is high
low= affinity of ligand for receptor is very high high= the affinity of the ligand for the receptor is very low
what is equilibrium
a state of balance due to the equal action of opposing forces
what is Le Chateliers principle
we can force a change in equilibrium by changing concentration of either A or B
what is the EF hand
a protein motif associated with calcium binding
what is a motif
a conserved amino cid sequence
what characterises the EF hand
a helix-loop-helix configuration
what is the KD of an EF hand
~ 10^-6 M
how does EF hand bind to calcium
acidic amino acid residues have carboxylate oxygen ligands- these act as ligands for metal ions such as calcium
how many residues in a EF hand
29 residues
which residue permits a sharp bend in the loop
Gly at position 15
what does calmodulin stand for
calcium modulated protein
how many EF hands in calmodulin
4
what occurs in calmodulin when calcium binds
change in shape, it is now able to bind and activate kinases
name 2 functions of calcium
- secondary messenger in muscle contraction
- controls release of hormones and neurotransmitters
describe the structure of calmodulin
- dumb-bell shape
- N- and C- terminal domains each have 2 EF hands separated by a 6-turn alpha helices
true or false:
calmodulin’s occur in 4s
false: occur in pairs
what happens when one EF hand binds calcium
becomes easier for the other EF hand in the same domain to bind a calcium
= COOPERATIVE CALCIUM BINDING
what is an apo structure
one that is missing its ligand or binding partner
how is the structure of apo calmodulin different to calmodulin
- flexible and dynamic molecule
- region between N and C terminal is folded and packed together
what happens when 4 calcium molecules bind on calmodulin
a conformational change occurs, exposing a hydrophobic patch, this allows interaction with other proteins
what is the function of the hydrophobic patch
when exposed allows interaction with other proteins
give examples of target molecules for calmodulin
phosphorylase kinase
adenylate cyclase
ca2+ATPase
