Self-association of streptococcus pyogenes collagen-like constructs into higher order structures

Area of Science:

• Biochemistry
• Structural Biology
• Biomaterials Science

Background:

• Bacterial collagen-like proteins (CLPs) can form stable triple helices despite lacking hydroxyproline (Hyp).
• Streptococcus pyogenes possesses a cell surface protein with collagenous domains.

Purpose of the Study:

• To investigate the structural properties and self-assembly potential of recombinant collagen-like proteins from Streptococcus pyogenes.
• To explore the role of hydroxyproline absence in bacterial collagen triple-helix formation and fibril assembly.

Main Methods:

• High-yield cold-shock expression system for producing recombinant V-CL and V-CL-CL proteins.
• Characterization of triple-helix stability using thermal transitions and calorimetric enthalpy measurements.
• Analysis of molecular assembly using SLS crystallite formation and electron microscopy.

Main Results:

• Purified V-CL and V-CL-CL proteins formed stable triple helices with sharp thermal transitions (35-37°C) and high enthalpy.
• SLS crystallite formation revealed ordered arrays of V-CL-CL molecules and dimer formation via globular domains.
• Isolated collagen domains (CL, CL-CL) self-assembled into fibrillar structures (4-5 nm diameter) without hydroxyproline.

Conclusions:

• The collagen triple-helix domain of this S. pyogenes protein can form stable structures and fibrillar assemblies independently of hydroxyproline.
• Bacterial collagen-like proteins exhibit self-assembly properties with potential for biomaterials and tissue engineering.
• The findings challenge the necessity of hydroxyproline for collagen triple-helix stability and fibril formation.