Protein-macrocycle framework engineering: supramolecular copolymerisation with two disparate calixarenes

ABSTRACT

Water soluble calixarenes are versatile mediators of protein assembly, including the fabrication of crystalline frameworks. Here, we report the X-ray crystal structure of cytochrome c (cytc) co-crystallised with two different calixarenes: phosphonato-calix[6]arene (pclx₆) and sulfonato-calix[8]arene (sclx₈). Each calixarene type acts as an independent molecular glue that mediates cytc dimers within the crystal. The calixarene-mediated dimers combine to yield chains of cytc-sclx₈-cytc-pclx₆-pclx₆ repeating units. These supramolecular copolymer units pack together, via a protein-protein interface, to yield a porous dendrite-like assembly. Interestingly, the tri-component framework has features in common with previously reported structures of cytc in complex with pclx₆ or sclx₈. Known protein-calixarene ‘building blocks’ combine in novel ways to yield the tri-component assembly, highlighting the versatility of calixarene molecular glues in protein crystal engineering.

Graphical abstract

KEYWORDS:

• Conformation
• crystal engineering
• molecular glue
• recognition
• self-assembly

Acknowledgments

We thank NUI Galway, the Australian Research Council and Science Foundation Ireland for funding. The authors would like to thank SOLEIL synchrotron (Paris) for beam time allocation, and the staff at beam line PROXIMA-2A for their assistance with data collection.

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by NUI Galway (College of Science and Engineering postgraduate scholarship to NMM), the Australian Research Council (Discovery grant to CLR) and Science Foundation Ireland (grants 13/CDA/2168 and 12/RC/2275_P2 to PBC).