Chain alignment of collagen I deciphered using computationally designed heterotrimers

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Collagen I (COL1) is the most abundant collagen, crucial for tissue structure.
• COL1 comprises one unique chain B and two similar chain A polypeptides forming a heterotrimeric triple helix.
• The precise positioning of chain B within the COL1 triple helix has remained unresolved for decades.

Purpose of the Study:

• To determine the definitive register of chain B within the Collagen I heterotrimeric triple helix.
• To investigate the impact of chain B's position on protein recognition and cellular signaling.

Main Methods:

• Designed and synthesized three Collagen I heterotrimeric triple helix variants with chain B in leading (BAA), middle (ABA), and trailing (AAB) positions.
• Incorporated putative von Willebrand factor (VWF) and discoidin domain receptor (DDR) recognition sequences into the designed heterotrimers.
• Assessed the binding affinity of each variant to VWF and DDR, and measured cellular DDR phosphorylation levels.

Main Results:

• The AAB heterotrimer, with chain B in the trailing position, exhibited a strong preference for binding both VWF and DDR.
• Cellular assays showed that the AAB conformation induced significantly higher levels of DDR phosphorylation.
• These findings provide strong evidence for the AAB register as the functional conformation of Collagen I.

Conclusions:

• This study resolves the long-standing debate regarding the position of chain B in Collagen I.
• The Collagen I AAB register is critical for mediating interactions with VWF and DDR, influencing cellular signaling pathways.
• Understanding the precise COL1 structure has implications for biomaterial design and therapeutic strategies targeting collagen-mediated processes.