Fibrous proteins

Question 1

What is the structure of fibrous proteins

Answer 1

Fibrous proteins are made of 3 alpha chains which go around one another and is held together by interchain hydrogen bonds

Question 2

What is the most common form of collagen and its composition

Answer 2

Collagen type 1, 2 alpha1 chains and 1 alpha2 chain

Question 3

3 types of collagen

Answer 3

Fibril forming, network forming. fibril associated

Question 4

Where are type 1, 2 and 3 collagen mainly found

Answer 4

Type 1 is found in tendons or corneas that require high tensile strength. Type 2 in cartilaginous structures, type 3 in blood vessles

Question 5

What are network forming collagens

Answer 5

Type 4 and Type 8, forming 3D mesh rather than distinct fibrils. Type 4 makes the basement membrane

Question 6

What are Fibril associated collagen

Answer 6

Type 9 and type 12, bind to collagen fibril surface, linking the fibrils to one another and to the ECM

Question 7

What is the difference in structure between globular and fibrous proteins

Answer 7

Globular proteins are compact while fibrous proteins are elongated, triple helical structures held together by interchain hydrogen bonds

Question 8

What 2 amino acids are found in collagen

Answer 8

Proline and glycine

Question 9

What are hydroxyproline and hydroxylysine

Answer 9

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.

Question 10

What things are needed for hydroxylation to occur

Answer 10

molecular oxygen, ferrous iron Fe2+, reducing agent vitamin C

Question 11

What are the different distributions of collagen

Answer 11

Fibril forming, network forming, fibril associated

Question 12

Where are type 1, 2 and 3 cartilage found

Answer 12

Type 1 is found in high tensile strength areas like tendons, type 2 in cartilaginous structures, type 3 in blood vessels

Question 13

What is the amino acid structure of collagen

Answer 13

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

Question 14

What is the importance of hydroxyproline and hydroxylysine

Answer 14

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

Question 15

How does synthesis of collagen happen

Answer 15

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

Question 16

What is the problem of EDS on collagen and what causes it

Answer 16

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

Question 17

What is the cause and symptoms of OI

Answer 17

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

Question 18

Elastin properties

Answer 18

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

Question 19

What is the cause of A1AT

Answer 19

Purine base substitution of GAG to AAG, lysine instead of glutamic acid instead of lysine