Fig. 1.

C-Pro domain-mediated assembly of collagen type-I. a Schematic representation of collagen-I assembly. Two strands of Colα1(I) and one strand of Colα2(I) typically assemble into heterotrimers, a process that is initiated by the respective C-Pro domains. Colα1(I) is also known to form homotrimers, whereas Colα2(I) does not homotrimerize and only forms heterotrimers. The crystal structure of a homotrimeric C-Pro domain is used here for illustration purposes (PDBID 5K31), with each collagen-I C-Pro domain differentially colored to demonstrate possible assembly schematics¹⁶. b Alignment of the Colα1(I) and Colα2(I) C-Pro domains highlights high sequence similarity. The cysteine network is numbered from C1 to C8 in the N-terminal to C-terminal direction, with each cysteine residue colored in red