Protein Assembly Flashcards
Fibrous proteins are not _______
water soluble
Fibrous proteins are use for body _____
construction
Predominant protein in elastic tissue
Elastin
Elastin has no ______, but is cross-linked via _______
Elastin has no regular secondary structure, but is cross-linked via lysines
Keratin contains ____ that are wound up so tightly in fibrils that it can’t ______
Keratin contains alpha-helices that are wound up so tightly in fibrils that it can’t digested
Elastin can be found in the _____
lungs
Keratin can be found in ____ and _____
hair and nails
Major fibrous protein of the human body
Collagen
Collagen has _____ called _____
3 polypeptide chains called alpha chains
3 different types of polypeptide chains are produced from ______
1, 2, or 3 different genes
Collagen type I is found in ____, _____, and ____
bone, skin, and tendon
Collagen Type III is ______. And it supports _____ in soft tissued
Collagen Type III is Reticulin. And it supports mesh in soft tissued
5 steps of Procollagen formation in fibroblast
1) Polypeptide chain synthesis
2) hydroxylation
3) glycosylation
4) Disulfide bond formation at C-terminus
5) Triple-helix formation
Central repeating region in collagen typically has these amino acids (3)
Glycine, Pr, Hyp (hydroxyproline)
During hydroxylation, several _____ and ____ (Amino acid) are hydroxylated in a post translational modification
prolines and lysine
Hydroxylation requires the enzymes _____ or _____
prolyl hydroxylase or lysyl hydroxylase with the co-factor ascorbic acid (vitamin C)
Improper hydroxylation causes ______ (due to lack of vitamin C)
scurvy
In Glycosylation, _____ are attached to _____
sugar molecules are attached to hydroxylysines
During disulfide bond formation _____ assemble
3 pro-alpha chains
______ is what is secreted from the fibroblast
pro collagen
After secretion, pro collagen is turned into ______
After secretion, pro collagen is turned into tropocollagen
During procollagen conversion to tropocollagen, _________
The N-terminal and C-terminal propeptidases are cleaved by procollagen peptidases to make collagen alpha-chains
The center part of tropocollagen has an unusual structure called _____
collagen helix
How do tropocollagen molecules assemble into a fibril?
Spontaneously. (Cleavage of propeptidases generated sticky ends)
What happens in Maturation through cross-links?
The enzyme lysyl oxidase catalyzes the formation of allysine residue from some lysine residues.
Fibrils are strengthened by cross-links between lysine and allylsine
What causes osteogenesis imperfects?
A glycine to cysteine substitution in the triple-helix region of Collagen type I
Mutations that affect collagen synthesis are dominant because
a mutation in one allele affects the function of all other alleles
There are two classes of molecular defects:
- Gene defects in the collagen genes (as described for Osteogenesis Imperfecta). DOMINANT
- Improper processing of collagen caused by lack of a processing enzyme (usually monomeric; defects occur when homozygous) RECESSIVE
4 synthesis Steps after pro collagen exists fibroblast
- Secretion
- N-terminal and C-terminal propeptides cleaved by pro collagen peptidases to make collagen alpha-chains. (forming tropocollagen)
- Tropocollagen molecules spontaneously assemble into a fibril
- Maturation through crosslinks
Examples of the transmissible spongiform encephalopathies caused by misfolded prion protein
- Mad Cow disease
* Creutzfeldt-Jakob disease
Two ways of acquiring the “bad” form of the prion protein.
- Inherit or acquire a missense mutation (classical Creutzfeldt- Jacob disease)
- Coming into contact with the “bad” form of the protein (new-variant Creutzfeldt-Jacob disease)
