Flashcards in MCBG - Post-Translational Modification (Secretory Pathway) Deck (21):
What sort of secretion is collagen?
What sort of secretion is insulin?
Give some examples of proteins delivered via the constitutive secretory pathway.
Immunoglobulins, albumin, prohormones, collagen, fibronectin, laminin, receptors
Give some examples of proteins delivered via the regulated secretory pathway.
Insulin, glucagon, beta-endorphin, ACTH, alpha-MSH, beta-lipotropin, trypsin
Where does the word "collagen" come from?
Greek "kolla" meaning glue
True or false - collagen is the most abundant protein in the body.
True - 25%-35% of all proteins
Which cells produce collagen?
How many polypeptide chains make up tropocollagen?
3 alpha polypeptide chains, each roughly 1000 aa long
True or false - collagen has a glycine in every fourth position along each alpha chain?
False - it's every third position
Give some characteristics of the triple helix structure of collagen.
- high tensile strength
Why is glycine the only amino acid that could be in the alpha chain in collagen?
Only amino acid with side chain small enough
The basic pattern of the alpha chain is this:
What is X usually?
Proline or hydroxyproline, can also be some Y positions
What shape is tropocollagen?
How are the alpha chains linked?
What does prolyl hydroxylase require to work?
Vitamin C and Fe2+
What is the result of having weak tropocollagen triple helices due to insufficient vitamin C?
How does prolyl hydroxylase strengthen the triple helices?
Hydroxylates residues, leading to formation of more H-bonds
What does lysyl oxidase require to work?
Vitamin B6 and Cu2+ ions
What does lysyl oxidase do?
Forms covalent cross-links between tropocollagens.
Why is tropocollagen secreted before final processing occurs?
It is too big and would destroy the cell if it were assembled within it