Circular permutation directs orthogonal assembly in complex collagen peptide mixtures.

Area of Science:

• Biochemistry
• Molecular Biology
• Bioinformatics

Background:

• Collagens are crucial extracellular matrix proteins that assemble into specific heterotrimers.
• The mechanisms governing heterospecific collagen assembly are not fully understood.
• Noncollagenous domains facilitate collagen folding, but sequence-level control of assembly is intriguing.

Purpose of the Study:

• To investigate whether collagen sequences can control heterospecific association.
• To design a model system for studying simultaneous assembly of two distinct collagen heterotrimers.
• To explore the evolutionary origins of fibrillar collagens.

Main Methods:

• Designed synthetic collagen peptides with optimized surface charge-pair interactions.
• Employed circular permutation to create modified collagen sequences.
• Analyzed assembly products using stoichiometry and structural preservation assessments.
• Performed bioinformatic analysis of natural collagen sequences.

Main Results:

• Circular permutation of collagen sequences preserved triple-helical structure and assembly specificity.
• A synthetic system demonstrated unprecedented heterospecificity, forming A:B:C and D:E:F heterotrimers (2 out of 56 possible stoichiometries).
• Natural collagen sequences show low similarity between neighboring exons.

Conclusions:

• Collagen sequences possess inherent capabilities for controlling heterospecific assembly.
• The synthetic model provides a powerful tool for studying collagen molecular recognition.
• Findings suggest fibrillar collagens may have evolved through duplication of smaller domains.