CB18: Proteins of ECM Flashcards
How many types of collagen are there?
28
What are the 4 most common types of collagen & where are they found?
Type I: found in skin, tendons & bones.
Type II: found in cartilage.
Type IV: found in basement membranes.
Type XI: found in bones & skin.
What is laminin?
A sheet-like network protein found in basement membranes that forms complexes with collagen type IV.
What is tenascin?
A protein that regulates tissue interactions during foetal development & oncogenesis.
What is fibronectin?
A protein involved in the guidance of migrating cells during embryogenesis & adhesion of cells to matrix.
What is 1 collagen molecule made of?
3 polypeptide alpha chains with glycine as the third amino acid.
How are collagen fibres made from collagen molecules?
Collagen molecules form covalent cross-links between lysine residues of collagen molecules. This forms collagen fibrils, which are then bound together to form collagen fibre.
How do collagen fibres form intermolecular cross-links?
The enzyme lysyl oxidase deaminates some lysines & hydroxylysines. This forms highly reactive aldehyde groups which can react with other lysines/hydroxylysines to form covalent bonds.
Where are intermolecular cross-links formed in collagen fibres?
In non-helical segments at the end of the molecules.
What is the role of proteoglycans in cartilage?
To resist compressive forces & allow rapid diffusion of nutrients, metabolites & hormones between blood & tissue cells.
What do proteoglycans do
They form ground substance to embed fibrous proteins.
How do proteoglycans give ground substance its gel-like consistency?
Proteoglycans are negatively charged so they attract cations and water is drawn in by osmosis, giving ground substance its gel-like consistency.
What are proteoglycans composed of?
Glycosaminoglycans linked to a core protein. They associate with each other & other components of ECM.
What are glycosaminoglycans?
They are polysaccharides composed of repeating disaccharides. They have sulphate/carboxyl groups so they are negatively charged.
What is the composition of the disaccharides in glycosaminoglycans?
- First disaccharide: amino sugar.
- Second disaccharide: uronic acid.
