The predominant roles of the sequence periodicity in the self‐assembly of collagen‐mimetic mini‐fibrils

Abstract

Collagen fibrils represent a unique case of protein folding and self‐association. We have recently successfully developed triple‐helical peptides that can further self‐assemble into collagen‐mimetic mini‐fibrils. The 35 nm axially repeating structure of the mini‐fibrils, which is designated the d ‐period, is highly reminiscent of the well‐known 67 nm D ‐period of native collagens when examined using TEM and atomic force spectroscopy. We postulate that it is the pseudo‐identical repeating sequence units in the primary structure of the designed peptides that give rise to the d ‐period of the quaternary structure of the mini‐fibrils. In this work, we characterize the self‐assembly of two additional designed peptides: peptide Col877 and peptide Col108rr. The triple‐helix domain of Col877 consists of three pseudo‐identical amino acid sequence units arranged in tandem, whereas that of Col108rr consists of three sequence units identical in amino acid composition but different in sequence. Both peptides form stable collagen triple helices, but only triple helices Col877 self‐associate laterally under fibril forming conditions to form mini‐fibrils having the predicted d ‐period. The Co108rr triple helices, however, only form nonspecific aggregates having no identifiable structural features. These results further accentuate the critical involvement of the repeating sequence units in the self‐assembly of collagen mini‐fibrils; the actual amino acid sequence of each unit has only secondary effects. Collagen is essential for tissue development and function. This novel approach to creating collagen‐mimetic fibrils can potentially impact fundamental research and have a wide range of biomedical and industrial applications.

Collagen Mimetic Peptides

“…In another peptide, peptide Col108rr, the sequences in each of the three SUs of Col108 were shuffled such that while the amino acid composition of this peptide was the same as Col108, the sequence periodicity was lost. As expected, the Col108rr only formed non-specific aggregates [ 170 ];…”

“…In another peptide, peptide Col108rr, the sequences in each of the three SUs of Col108 were shuffled such that while the amino acid composition of this peptide was the same as Col108, the sequence periodicity was lost. As expected, the Col108rr only formed non-specific aggregates [ 170 ]; In a new peptide, peptide Col877, the SU of Col108 was replaced by another 123 residues containing residues 877–986 of the α1 chain of human type I collagen [ 170 ] Thus, in contrast to Col108rr, Col877 had a very different amino acid composition from that of Col108, but had the same 123-residue sequence periodicity in its primary structure. Remarkably, Col877 can form mini-fibrils with the same 35-nm d -period as Col108.…”

“…In a new peptide, peptide Col877, the SU of Col108 was replaced by another 123 residues containing residues 877–986 of the α1 chain of human type I collagen [ 170 ] Thus, in contrast to Col108rr, Col877 had a very different amino acid composition from that of Col108, but had the same 123-residue sequence periodicity in its primary structure. Remarkably, Col877 can form mini-fibrils with the same 35-nm d -period as Col108.…”

Using sequence data to predict the self-assembly of supramolecular collagen structures

“…Recent studies show advancements in collagen mimetic peptide design, which has succeeded in obtaining collagen-mimetic trimers that are capable of self-assembly into periodic mini-fibers (44)(45)(46)(47). In these cases, sequence design is based on the selection of a fragment of a collagen helix, which is subsequently repeated in tandem (44)(45)(46)(47). Chen et al (45) have produced three collagen-mimetic helical peptides, two of which (designated by the authors as COL108 and COL877) have been shown experimentally to self-assemble into periodic structures.…”

Interaction Patterns for Staggered Assembly of Fibrils from Semiflexible Chains

“…Nevertheless, the fact that the staggered assembly is also found for collagen-I in-vitro (albeit not the same as in-vivo) does indicate that it is indeed encoded to some extent in the primary sequence. Further evidence in this direction also comes from studies on the assembly of engineered concatemers of (non-hydroxylated) fragments of collagen-I sequences, that form staggered fibrils, but with different gap sizes than natural collagen-I fibrils [11][12][13].…”