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Computational design of heterotrimeric collagen helices

As an important biomedical material, collagen has been widely used in wound sutures, cartilage defect filling, and bone metal implant coating. Seven out of the twenty-eight types of natural collagen are heterotrimers comprising three chains with different primary sequences. It is important to understand the intermolecular forces underlying the hetero-specific assembly of natural collagen to modulate material properties in protein engineering and biomaterials engineering. Till date, the most important pairwise interaction identified in the collagen triple helix is the axial charge pair, which can be formed between appropriately placed lysine and aspartate or glutamate residues. These pairwise amino acid interactions enable the preparation of heterotrimeric helices with high specificity, as well as excellent control over helix structure and stability. Further, detailed studies on these interactions will allow the modification of natural collagen sequences to develop clean-sourced, highly controllable, and compositionally responsive collagen biomaterials. This review will summarize our understanding of this interaction and other charged-pair interactions and describe how they have been successfully used to control collagen triple helix self-assembly and explore new protein design strategies.