The Chain Register in Heterotrimeric Collagen Peptides Affects Triple Helix Stability and Folding Kinetics

Collagen type IV is a highly specialized form of collagen found only in basement membranes, where it provides mechanical stability and structural integrity to tissues and organs, and binding sites for cell adhesion. In its ubiquitous form, collagen type IV consists of two α1 chains and one α2 chain, whose internal alignment within the triple helix seems to exert a strong influence on the binding affinity to α1β1 integrin receptor. This has been assessed recently using two synthetic collagen peptides that contain the cell adhesion epitope of collagen type IV and are assembled into the most plausible α1α2α1′ and α2α1α1′ registers. In the present study, the effects of the chain register on the stability of the triple helix and the folding kinetics of these collagen peptides were investigated by CD spectroscopy and microcalorimetry. The results revealed a multi-domain structural organization for both trimers, with an unexpected strong effect of the chain alignment on the conformational stability. Molecular dynamics simulations served to rationalize more properly the experimental results.