Willmott 7 Collagen, Estrogen Receptor and Myoglobin

Question 1

COLLAGEN

Answer 1

• Provides tensile strength in: skin, bone,teeth, cartilage, etc
• 300 nm rod-shaped
• 3 polypeptides, each ~1000 amino acids
• Each chain has repeat -(Gly-X-Y)- pattern X usually Proline, Y often Hydroxyproline

Question 2

COLLAGEN

Glycine position & why

Answer 2

in 3rd position as small

-crosslinks

Question 3

Hydroxyproline, Vitamin C and Scurvy

Answer 3

linked

Question 4

Hydroxyproline (4-HyP) formed from …

Answer 4

…Proline under action of enzyme prolyl hydroxylase

Question 5

Additional –OH group allows ..

Answer 5

cross-links to form between chains, adds strength

Question 6

Prolyl hydroxylase requires ..

Answer 6

Ascorbic acid (= Vitamin C) as co-factor

Question 7

Insufficient vitamin C
=>

Answer 7

Pro not converted to 4-HyP
= > No cross-links
= > weak collagen
=> scurvy

Question 8

Estrogen Receptor (ER)
function:
type of protein:

Answer 8

Regulates response to estrogen (oestrogen)

• Soluble protein, nuclear hormone receptor => hydrophobic => more through memb. In cytoplasm

Question 9

Estrogen Receptor (ER)
To achieve effect needs 2 key domains:
-

Answer 9

:
- ligand-binding domain (binds hormone) - DNA-binding domain

Question 10

ER binds to

Answer 10

specific DNA sequences (= estrogen response elements)

• Affects transcription of neighbouring genes

Question 11

ER overproduced in

Answer 11

~70% breast cancers = “ER positive”
•

Question 12

Tamoxifen

Answer 12

competes for binding to ER, but does not activate

Question 13

Antibreast cancer drug =>

Answer 13

helix 12 made unstable => coActivater can’t bind

Question 14

Myoglobin (Mb)
function:
size:
subunits:
Contains:

Answer 14

Oxygen-storing protein in muscle
153 amino acids (18 kDa) => small easily obtained from tissue
Contains a single subunit
Contains essential “prosthetic group” * 
(haem - with Fe atom)


Question 15

Ferrous

Answer 15

(Fe2+) in haem

Question 16

Ferric

Answer 16

(Fe3+) does not bind oxygen

Question 17

Histidines involved in

Answer 17

O2 binding in myoglobin

Question 18

Carbon monoxide

Answer 18

binds permanently

Question 19

Prosthetic group:

Answer 19

compound permanently associated with a protein that contributes to the protein’s function

Question 20

O2 binding to myoglobin

Eq

Answer 20

Mb + O2 MbO2

Question 21

dissociation equilibrium constant:

Answer 21

Kd= [P] . [L] /
[PL]

= [Mb] . [O2] /
[MbO2]

Question 22

O2 binding to myoglobin
Fractional Saturation (Y) =

Answer 22

binding sites occupied/ total binding sites

[MbO2] /
[Mb] + [MbO2]
Can be rearranged to...
Y=
[O2]
/
 Kd + [O2]

Question 23

Myoglobin saturation curve is

Answer 23

hyperbolic