Question

List the steps in the synthesis of type I collagen, starting with the mRNA and ending with the cross-linked extracellular fibril. For each step that you list, state whether that step is typical for most secreted proteins, or whether that step is specific to collagens.

I know the steps but I don't know which ones are for most proteins and which one are only for collagen.

Answer 1

Collagen is a protein molecules made up of aminoacids.It provide structural support of connective tissues.Collagen can be found in different group depending on their type of structure.The most common type of collagen is Type I collagen.

STEPS INVOLVED IN THE SYNTHESIS OF TYPE I COLLAGEN

It involves 3 steps 1.Transcription of mRNA in the nucleus

                          2. Transilation

                          3. post- transilation modification

1. Transcription of mRNA in the nucleus- Pro a1 and pro a 2 chain are transcribed in this step.

2. Transilation- mRNA intract with ribosome for transilation

3. post transilation modification-

• Pre-pro polypeptide undergo post transilation and to become pro- collagen.
• The signal peptide is removed on the N- terminal
• The lysine and proline residue get additional hydroxyl group added to them which require vitamin C as a cofactor
• glycosilation occurs in hydroxyl group on glycene with galactose and glucose b.
• 3 Hydroxylated and glycosilated pro a chain assemble by twisting into tripple helix to form zipper like folding
• Final modification.
• Prolin lysine are aminoacids

PROTEIN INVOLVED IN TYPEI COLLAGEN SYNTHESIS

Collagen attached to the membrane of cell via different types of protein, including fibronectin, laminin, fibulin and integrin.

Fibronectin is a protien. Transilation with wild type pro alpha 1 collagen gene resulted in the production of extensive matrix containing fibronectin.Aminoacids involved in fibronectin collagen intraction mutation were introduced into fibronectin binding region of pro a 1 collagen gene.

Fibulin belongs to extracellular matrix protein.Fibulin 1 has many protein intraction with other PCM Protein, including fibroncetin, fibrinogen and component of the basement membrane.

Integrin mediated cell adhision to Type I collagen.Two members of the sub group a1b1 and a2b2 integrins are bind to monomeric form of Type I collagen.collagen- integrin association can be analysised only through immunoelectron microscopy.Intigrin a21 domain is able to bind to D- banded type I collagen fibrils.