The structural basis for the collagen processing by human P3H1/CRTAP/PPIB ternary complex.

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Medicine

Background:

• Collagen posttranslational modification is essential for tissue integrity.
• Defects in collagen processing cause disorders such as osteogenesis imperfecta (OI).
• The structural basis of the P3H1/CRTAP/PPIB collagen processing complex remains elusive.

Purpose of the Study:

• To elucidate the structural organization and mechanism of the P3H1/CRTAP/PPIB complex.
• To understand how this complex processes collagen.
• To provide insights into the molecular pathology of collagen-related disorders.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures of the P3H1/CRTAP/PPIB complex.
• Structures were determined for the complex alone and in complex with a collagen peptide.
• Mutagenesis and inhibitor studies were performed to investigate complex dynamics.

Main Results:

• The active sites of P3H1 and PPIB form a bifunctional reaction center, suggesting coupled modification.
• Multiple collagen peptide binding sites were identified, indicating a substrate interaction zone.
• A dual-ternary complex was observed, with its equilibrium sensitive to mutations and PPIB inhibitors.

Conclusions:

• The study provides high-resolution structures of the P3H1/CRTAP/PPIB complex, revealing its mechanism of action.
• These findings offer a structural basis for understanding collagen processing and OI pathogenesis.
• The identified dual-ternary complex and its regulation provide new avenues for therapeutic intervention.