Fibrous proteins

Question 1

In the Gly-x-y structure of collagen, x is most likely

Answer 1

Proline

Facilitates formation of orientation of each alpha helical chain

Question 2

Y in the sequence is usually

Answer 2

Hydroxy lysine or hydroxy proline

Question 3

Why Glycine ?

Answer 3

Fits into small space in center of tightly packed tropocollagen triple helix

Question 4

Hydroxy lysine and hydroxy proline are formed during

Answer 4

Post translational protein modification of proline and lysine by hydroxylation

Question 5

Which enzyme required for hydroxylation

Answer 5

Prolyl and lysyl hydroxylase

In addition to ascorbate and o2(co factors)

Question 6

Function if hdp residue

Answer 6

Hydrogen bonding. Stabilizes tropocollagen triple helix

Question 7

Role of hdl residue

Answer 7

Cross link formation (covalent cross link)

Stabilizes collagen

Question 8

Osteolathyrism caused by…

Answer 8

Inhibition of lysyl oxidase (which converts hydroxylysine to a more reactive hydroxyallysine for formation of cross link)

Question 9

What point mutation brings about osteogenesis imperfecta

Answer 9

Glycine-cysteine substitution

Question 10

Structure if elastin fiber?

Answer 10

Consists of multiple tropoelastin monomers cross linked together by lysyl oxidase

Lysine cross link(desmosine)

4 way cross link

Question 11

Aa composition of elastin

Answer 11

Gly Pro Ala Val