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Updated: May 16, 2026
11:34
Investigating Receptor-ligand Systems of the Cellulosome with AFM-based Single-molecule Force Spectroscopy
Published on: December 20, 2013
Single-molecule dissection of the high-affinity cohesin-dockerin complex
Stefan W Stahl1, Michael A Nash, Daniel B Fried
1Lehrstuhl für Angewandte Physik, Center for NanoScience and Center for Integrative Protein Science, Ludwig-Maximilians-Universität, 80799 Munich, Germany.
Summary
Cellulosomes, complex enzyme structures, exhibit exceptionally strong protein-protein interactions. Understanding these molecular interactions is key to advancing biofuel production and other industrial applications.
Area of Science:
- Biochemistry
- Molecular Biology
- Bioengineering
Background:
- Cellulose-degrading enzyme systems are crucial for industrial applications like biofuel production.
- Cellulosomes are complex, multimodular extracellular enzyme complexes from anaerobic bacteria.
- The assembly of cellulosomes relies on interactions between cohesin and dockerin modules.
Purpose of the Study:
- To analyze the mechanical stability of cohesin-dockerin interfaces in cellulosomes using single-molecule force spectroscopy.
- To investigate the role of calcium ions and specific amino acid residues in maintaining these high-affinity interactions.
Main Methods:
- Employed single-molecule force spectroscopy to measure the rupture forces of cohesin-dockerin interactions.
- Utilized atomic force microscopy to quantify single-molecule binding and observe force-induced calcium dissociation.
- Investigated the effect of calcium chelation (EDTA) and a specific cohesin mutation (D39A) on interaction stability.
Main Results:
- Observed exceptionally high rupture forces (>120 pN) for cohesin-dockerin interactions, indicating remarkable mechanical stability.
- Demonstrated that force-induced dissociation of calcium ions from the dockerin's F-hand motif weakens cohesin binding.
- Showed that a cohesin mutation disrupting hydrogen bonds with dockerin serine residues reduces rupture forces and maintains dockerin activity during dissociation.
Conclusions:
- Cohesin-dockerin interactions represent a highly stable class of protein-protein interactions crucial for cellulosome assembly.
- Calcium ions play a critical role in the stability and regulation of these interactions.
- Insights into these single-molecule mechanics inform the design of cellulose-degrading molecular machines for biotechnological applications.
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