Fibrous proteins Flashcards
Which are the three classes of fibrous proteins?
- silk (aka fibroin)
- a-keratin
- collagen
Which folding motif is common in keratins and how does it look?
coiled-coil motifs, which bascially means helix out of helix.
The motif is a helical wheel which repeats in a specific pattern
Which pattern does coiled-coil motifs repeat in?
HPPHCPC
H= hydrophobic
P= polar
C = charged
What type of fibrous proteins forms intermediate filaments?
keratin
How does a-keratin create long structures?
a-keratin creates crosslink S-S bonding from cystein
In what non-keratin based proteins are coiled-coil motifs common?
Receptors and viruses
What pattern does silk consist of?
(G-S-G-A-G-A)n
How is silk arranged?
By antiparallell b-strands which is arranged along the fiber forming a microcrystalline array
What aa are predominant in collagen and what is the secondary structure called?
Gly, Pro and Hyp (Proline with OH-group)
Tripple helix
How many residues per turn does tripple helicies have?
3,3 res/turn
How is the tripple helix stabilized?
Van der Waals interactions as well as H-bonds between polypeptide chains. Also hydroxylation of proline (and lys) increases the stability (more H-bonds)
What is scurvey?
Vitamin C defficiency
What cofactor is needed for synthesis of collagen?
Vitamin C
What does hydroxylation of pro and lys do in collagen?
Increases stability and crosslinking within and between collagen molecules in a fibril
