Deciphering the folding code of collagens
Jean‐Daniel Malcor, Noelia Ferruz, Sergio Romero‐Romero, Surbhi Dhingra, Vamika Sagar, Abhishek A. Jalan
Abstract
Collagen proteins contain a characteristic structural motif called a triple helix. During the self-assembly of this motif, three polypeptides form a folding nucleus at the C-termini and then propagate towards the N-termini like a zip-chain. While polypeptides from human collagens contain up to a 1000 amino acids, those found in bacteria can contain up to 6000 amino acids. Additionally, the collagen polypeptides are also frequently interrupted by non-helical sequences that disrupt folding and reduce stability. Given the length of polypeptides and the disruptive interruptions, compensating mechanisms that stabilize against local unfolding during propagation and offset the entropic cost of folding are not fully understood. Here, we show that the information for the correct folding of collagen triple helices is encoded in their sequence as interchain electrostatic interactions, which likely act as molecular clamps that prevent local unfolding. In the case of humans, disrupting these electrostatic interactions is associated with severe to lethal diseases. Collagen triple helices are found in all the three domains of life as well as viruses. Here, the authors show that collagens have converged on a similar folding mechanism that employs salt bridge interactions to guide the triple helix assembly.