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
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).