Fibrous proteins Flashcards
What is the structure of fibrous proteins
Fibrous proteins are made of 3 alpha chains which go around one another and is held together by interchain hydrogen bonds
What is the most common form of collagen and its composition
Collagen type 1, 2 alpha1 chains and 1 alpha2 chain
3 types of collagen
Fibril forming, network forming. fibril associated
Where are type 1, 2 and 3 collagen mainly found
Type 1 is found in tendons or corneas that require high tensile strength. Type 2 in cartilaginous structures, type 3 in blood vessles
What are network forming collagens
Type 4 and Type 8, forming 3D mesh rather than distinct fibrils. Type 4 makes the basement membrane
What are Fibril associated collagen
Type 9 and type 12, bind to collagen fibril surface, linking the fibrils to one another and to the ECM
What is the difference in structure between globular and fibrous proteins
Globular proteins are compact while fibrous proteins are elongated, triple helical structures held together by interchain hydrogen bonds
What 2 amino acids are found in collagen
Proline and glycine
What are hydroxyproline and hydroxylysine
Hydroxyproline is non-stranded amino acids that are found in the peptide chain. They form due to hydroxylation of proline or lysine and are post transitional modifications.
What things are needed for hydroxylation to occur
molecular oxygen, ferrous iron Fe2+, reducing agent vitamin C
What are the different distributions of collagen
Fibril forming, network forming, fibril associated
Where are type 1, 2 and 3 cartilage found
Type 1 is found in high tensile strength areas like tendons, type 2 in cartilaginous structures, type 3 in blood vessels
What is the amino acid structure of collagen
Collagen is rich in proline and glycine, proline forms the helical structure due to the kink in the alpha chain causing the structure to not be an alpha helix, glycine fits into small areas in every 3rd position forming Gly-X-Y, X for proline and Y is hydroxyproline or hydroxylysine
What is the importance of hydroxyproline and hydroxylysine
Hydroxyproline forms inter chain hydrogen bonds, it is formed from prolyl hydroxylase and hydroxylysine is glycosylated in the hydroxy group prior to triple helix formation
How does synthesis of collagen happen
Prepro alpha chains are the precursors for a chain, which contain special amino acids in the N terminal that allow for attachment to RER and passage into lumen of RER where the N terminal is cleaved to form pro alpha chains, precursor to collagen.
Hydrocylation which is done by prolyl hydroxylase and lysyl hydroxylase, it requires molecular oxygen, Fe2+and vitamin C, when glycosylation does not occur we have inter chain hydrogen bonds impaired, glycosylation also occurs
Assembly and secretion of pro alpha chains which form into the triple helix called procollagen, rest you know
What is the problem of EDS on collagen and what causes it
It is caused by deficiency of collagen processing enzymes such as lysyl hydroxylase and N procollagen peptidase, Type V collagen cause extending oh skin and hyper mobility of joint, type 3 is the most serious form that causes arterial rupture
What is the cause and symptoms of OI
OI is caused by glycine in alpha 1 or alpha 2 chain to be replaced by bulky side chain, preventing formation of triple helical structure
Type 1 is most common, causes blue sclera, brittle bone and hearing loss
Type 2 is most severe in perinatal period by pulmonary complications
Type 3 is also severe causes short stature and kyphotic curvature
Elastin properties
Elastin is made of tropoelastin, it does not contain as much hydroxyproline or hydroxylysine, lysyl oxidase delaminates lysine residues to form allysine, 3 allysine residues and one lysine residue combine to form demosine cross link
What is the cause of A1AT
Purine base substitution of GAG to AAG, lysine instead of glutamic acid instead of lysine
