Olivier Hamelin, Philippe Carpentier

Few years ago, the crystal structure of the Sterile Alpha Motif domain of the LEAFY protein from Ginkgo biloba (GbLFY-SAM, LEAFY WT), a transcription factor involved in plant meristem division and differentiation, was solved. Each monomer (111 amino-acid residues without any cysteine) interacts the following one via head-to-tale interaction resulting in a helix-shaped oligomer. This latter interlocks with six others leading to a crystalline honeycomb architecture showing parallel nanotubes with interesting features. First, the size of the resulting crystal needles, 0.3-0.5 mm long and about 40 µm wide, make them easy to handle. Then, the tubes size diameter of about 5 nm allows the diffusion of many molecules. Finally, it was shown that a 38 residues C-terminal side chain by monomers is positioned and accessible in the interior of the tubes and thus could be used as original and modular grafting platforms to generate new and original biohybrid materials.




Recently, we successfully exploited this property for the controlled grafting of a ruthenium complex on the LEAFY_K84C mutant where the lysine 84 localized in the side chain was replaced by a cysteine as unique binding site. More importantly, the resulting material shows an extraordinary increase in stability in both organic and aqueous acidic media. This property is of importance for the development of stable crystalline functional bio-hybrid materials for heterogeneous catalysis, since protein crystals usually display an inherent fragility and need to be further stabilized by cross-linking strategy in order to serve in chemical applications.




Reference:
Chiari L, Carpentier P, Kieffer-Jaquinod S, Gogny A, Perard J, Ravanel S, Cobessi D, Ménage S, Dumas R and Hamelin O
LEAFY protein crystals with a honeycomb structure as a platform for selective preparation of outstanding stable bio-hybrid material.
Nanoscale, 2021, 13(19): ​8901-8908​