Fibrous Proteins Flashcards
what 3 types of molecules are found in ecm of all tissues
1- proteogylcans
2- collagens
3- multiadhesive matrix proteins
what are the two types of proteins in the body
Fibrous
Globular
what are the 3 types of fibrous proteins
alpha keratin - external protection
elastin - in connective tissues
collagen - also in connective tissues but related to tensile strength
what cells are alpha keratin made by
epidermal cells
describe the secondary structure of alpha keratin
alpha helices
rich in amino acids
hydrophobic side chains on the outside that make it insoluble
rich in cys residues which form disulphide bridges between cysts in separate alpha helices to connect them
explain the role of disulphide bridges
stabilise the interior of a globular protein and make alpha keratin stronger
what is a protofibril
when a dimer associates antiparallel with two other dimers in a staggered arrangement
what is elastin made from
fibroblasts and chondrocytes
describe formation of elastin
proelastin to tropoelastin
tropoelastin crosslinked via LYSINE residues to give elastin
what are the two types of cross links that occur
desomsine - 4 lysine
aldol/lysinonorleucine - 2 lysine
these links are formed by oxidation
describe desmosine cross link
formed from 4 lysines 3 of which are oxidised
how can elastin deform
because it has a lack of hydrogen bonds
what is the secondary structure of elastin
beta spiral
what is the most abundant protein in the body
collagen
what cells make collagen
fibroblasts and chondrocytes
what are the 4 stages of collagen assembly
1- synthesised as procollagen which is secreted from the cell
2- cleaved to tropocollagen by procollagen peptidase
3 - assembly of tropocollagen leads to collagen fibre
then crosslinking strengthens
triple helix structures
what type of triple helix is found in collagen
left handed helix (alpha helices are usually right handed
does collagen have hydrogen bonds
yes - unlike elastin
what property of the polypeptide allows them to be packed together in collagen
glycine R-group is only H
allows chains to be packed together
what is the role of the pro and hyp residues on the outside of the helices
they form inter-triple helix contacts to stabilise the collagen fibres
what is osteogenesis imperfecta
mutant collagen gene Gly becomes Cys problem with procollagen formation tropocollagen not regularly packed as it remains unfolded clinical symptom - brittle bones
what is ehlers - danlos syndrome
reduced levels of procollagen peptidase
procollagen is not fully converted to tropocollagens
stretchable skin - imperfect collagen
what is scurvy
hydroxyproline needed for correct assembly of collagen - needed for OH group
vitamin c ascorbate is a cofactor for this
leads to skin lesions and damages blood vessels
what is lathyrism
it effects the final stages of crosslinking
copper deficiency or ingestion of beta-aminopropionitrile
irreversibly inhibits lysyl oxidase
