Formation of Type I collagen
Within the cell
During translation, two types of peptide chains are formed on ribosomesalong the rough endoplasmic reticulum (RER). These are called the alpha-1 and alpha-2 chains. These peptide chains (known as preprocollagen) have registration peptides on each end and a signal peptide.
The preprocollagenis then released into the lumen of the RER. Thereafter the signal peptides are cleaved inside the RER and the peptide chains are now called pro-alpha chains.