The evolutionary advantage of an aromatic clamp in plant family 3 glycoside exo-hydrolases

Sukanya Luang , Xavier Fernández-Luengo , Alba Nin-Hill , Victor Streltsov , Julian Schwerdt , Santiago Alonso-Gil , James Ketudat Cairns , Stéphanie Pradeau (1) , Sébastien Fort (1) , Jean-Didier Maréchal , Laura Masgrau , Carme Rovira , Maria Hrmova

1 CERMAV - Centre de Recherches sur les Macromolécules Végétales

In the barley β- d -glucan glucohydrolase, a glycoside hydrolase family 3 (GH3) enzyme, the Trp286/Trp434 clamp ensures β- d -glucosides binding, which is fundamental for substrate hydrolysis during plant growth and development. We employ mutagenesis, high-resolution X-ray crystallography, and multi-scale molecular modelling methods to examine the binding and conformational behaviour of isomeric β- d -glucosides during substrate-product assisted processive catalysis that operates in GH3 hydrolases. Enzyme kinetics reveals that the W434H mutant retains broad specificity, while W434A behaves as a strict (1,3)-β- d -glucosidase. Investigations of reactant movements on the nanoscale reveal that processivity is sensitive to mutation-specific alterations of the tryptophan clamp. While wild-type and W434H utilise a lateral cavity for glucose displacement and sliding of (1,3)-linked hydrolytic products through the catalytic site without dissociation, consistent with their high hydrolytic rates, W434A does not adopt processive catalysis. Phylogenomic analyses of GH3 hydrolases disclose the evolutionary advantage of the tryptophan clamp that confers broad specificity, high catalytic efficiency, and processivity.

Domaines: Chimie organique; Sciences du Vivant [q-bio]

Sukanya Luang, Xavier Fernández-Luengo, Alba Nin-Hill, Victor Streltsov, Julian Schwerdt, et al.. The evolutionary advantage of an aromatic clamp in plant family 3 glycoside exo-hydrolases. Nature Communications, 2022, 13 (1), pp.5577. ⟨10.1038/s41467-022-33180-5⟩. ⟨hal-03787779⟩