Discovery of processive catalysis by an exo-hydrolase with a pocket-shaped active site.

Streltsov, Victor A.; Luang, Sukanya; Peisley, Alys; Varghese, Joseph N.; Cairns, James R. Ketudat; Fort, Sebastien; Hijnen, Marcel; Tvaroška, Igor; Ardá, Ana; Jiménez-Barbero, Jesús; Alfonso-Prieto, Mercedes; Rovira, Carme; Mendoza, Fernanda; Tiessler-Sala, Laura; Sánchez-Aparicio, José-Emilio; Rodríguez-Guerra, Jaime; Lluch, José M.; Maréchal, Jean-Didier; Masgrau, Laura; Hrmova, Maria

Substrates associate and products dissociate from enzyme catalytic sites rapidly, which hampers investigations of their trajectories. The high-resolution structure of the native Hordeum exo-hydrolase HvExoI isolated from seedlings reveals that non-covalently trapped glucose forms a stable enzyme-product complex. Here, we report that the alkyl β-D-glucoside and methyl 6-thio-β-gentiobioside substrate analogues perfused in crystalline HvExoI bind across the catalytic site after they displace glucose, while methyl 2-thio-β-sophoroside attaches nearby. Structural analyses and multi-scale molecular modelling of nanoscale reactant movements in HvExoI reveal that upon productive binding of incoming substrates, the glucose product modifies its binding patterns and evokes the formation of a transient lateral cavity, which serves as a conduit for glucose departure to allow for the next catalytic round. This path enables substrate-product assisted processive catalysis through multiple hydrolytic events without HvExoI losing contact with oligo- or polymeric substrates. We anticipate that such enzyme plasticity could be prevalent among exo-hydrolases.

Nature Communications, 2019, Vol 10, Issue 1, p1

2041-1723

Academic Journal

10.1038/s41467-019-09691-z