Fibrous Proteins

Question 1

alpha-Keratins

Answer 1

Alpha helices w/ 7 residue psuedorepeat with 1 and 4 being hydrophobic to create “sticky strip” leading to coiled-coil formation.

Stabilized with disulfide bonds.

Question 2

Collagen

Answer 2

Most abundant protein in body made up of Gly-X-Y repeats w/ high contents of proline and lysine. Helical, but not alpha helix – left handed!!

Pre-pro alpha chains translated in RER and proline / lysine hydroxylated w/ Vit C and Fe2+ –> glycosylation of lysine –> formation of triple helix procollagen –> secreted into ECM where procollagen peptidases remove C and N terminal –> covalent crosslinks by lysyl oxidase requiring Cu2+ forms collagen fibers

Question 3

Type 1 Collagen

Answer 3

Bone, skin, tendons, ligaments, cornea

Diseases: OI, EDS

Question 4

Type 2 Collagen

Answer 4

Cartilage

Diseases: Collagenopathy

Question 5

Type 3 Collagen

Answer 5

Blood vessels, skin

Diseases: Vascular EDHS, Dupuytren’s contracture

Question 6

Type 4 Collagen

Answer 6

Basal lamina

Diseases: Alport syndrome, goodpasture’s syndrome

Question 7

Type 5 Collagen

Answer 7

Same as Type 1

Diseases: Classical EDS

Question 8

Elastin

Answer 8

Polypeptide chain rich in gly, ala and val structured in random coils crosslinked by lysyl oxidase.