Extracellular Matrix Proteins Flashcards
Types I to IV account for what % of human collagen?
Over 90%
What are the tissues associated with collagens type I through IV?
I: Major component of Skin and Bone (also tendons)
II: Primarily in Cartilage
III: Found in blood vessels. Key role in wound healing
IV: Basement membrane of cells “basal lamina”
Mneumonic: SCVB: South Carolina Vetoed Bands
All collagens contain __ polypeptide chains. And all collagens have at least one ___.
3; triple helix domain
- Which 3 collagens have common structural characteristics?
- Each of these 3 collagen polypeptide chains has ~ ___ AA’s,
- each individual chain is called ___.
- Mature collagen of these has ___ ____.
- Every 3rd AA is collagen is ___.
- Collagen contains about 20%___ and ___.
- Collagen contains about __% hydroxylysine.
- Collagens I, II, III
- 1000
- alpha chain
- 3 alpha chains
- Glycine
- Proline;hydroxyproline
- 1-5%
Name 4 ways the collagen helix is VERY DIFFERENT from the alpha helix.
- It is more extended than an alpha helix
- It doesn’t have intrachain H bonds
- It’s stablized by steric repulsion of pyrrolidone rings
- The collagen helix is essentically a tertiary structure
- The collagen triple helix is rod-shaped. How long and wide is it?
- How are the 3 collagen strands bonded to each other?
- What else participates in interchain H bonds to further stabilize the triple helix?
- 3000 Angstroms long, 15 Angstroms wide.
- The strands are hydrogen bonded to each other via NH of glycine residue and CO of other residues.
- Hydroxyproline.
What is needed for hydroxylation of proline and lysine?
Ascorbic acid (aka vitamin C)
Hydroxylated ___ residues provide sites for ____.
Lysine; Glycosylation
What is the basic process for making mature collagen?
Translation will lead to procollagen formation, which is secreted and processed to form tropocollagen, which is then packed to form a collagen fibril, packed and stacked some more to form mature collagen.
How are collagen fibrils crosslinked?
Extracellular enzyme Lysyl Oxidase initiates crosslinking by forming aldehyde derivatives of lysine and hydroxylysine.
What even in sythensis of fibrous collagen happens just before the procollagen is secreted?
The triple helix of the 3 collagen strands are folded.
Cross linking involves nonenzymatic rxns b/w which 2 groups?
lysyl and allysl groups.
Where is Elastin found? Elastin is synthesized as what kind of precursor?
What is special about elastin?
It is found in elastic fibers of the ECM, and in elastic tissue like smooth muscle and lung. It is synthesized as a highly soluble tropoelastin precursor.
It has alternating hydrophilic and hydrophobic domains which contribute to its functional elasticity
Where does laminin bind to and crosslink other proteins?
In the basal laminae.
Laminin is ____ with ____ subunits.
These subunits form a ____ association domain.
heterotrimeric with alpha, beta, and gamma subunits.
They form a triple helix association domain.
What is special about the N-termini and C-termini of the subunits in laminin?
What is the function of this?
The triple helix association domain composing of 3 subunits all have N-terminal globular extensions, while only the alpha subunit has an additional C-terminal globular domain.
The globular domains interact w/ other cell surface proteins and conect the basal laminae to the cell.
What is a proteoglycan?
It is a polypeptide chain w/ lots of covalently bound polysaccharides.
NOTE: Polysaccharides make up 95% of of weight. They also provide a negative charge (they may be sulfated and carboxylated)
What do proteoglycans form?
They form a gel, which provides mechanical support, and allows diffusion of SMALL MOLECULES.
The gell has ECM proteins embedded in it.
What are the long unbranched polysaccharides of proteoglycans called?
Glycosaminoglycans (GAGs), composed of repeating disaccharide units that are frequently sulfated.
How is the GAG usually attached to the protein?
Where does glycosylation occur?
Via a Ser or Thr residue attached to a trisaccharide linker.
In the ER
Integrins are the major membrane protein that link cells to the ECM. What proteins do they attach to?
What is the structure of integrin protein?
Adehsion proteins like fibronectins;
Integrins are a dimer of alpha and beta subunits.
What can activation of integrin proteins cause?
Cell adhesion and cell migration (important for cancer)
Deficiency of vitamin C will cause____.
Scurvy
