The Crystal Structure of Nitrosomonas europaea Sucrose Synthase Reveals Critical Conformational Changes and Insights into Sucrose Metabolism in Prokaryotes

WU, R*; ASENCIÓN DIEZ, MD*; FIGUEROA, CM*; MACHTEY, MATIAS; IGLESIAS, AA; BALLICORA, MA; LIU, DALI

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Lugar: Washington; Año: 2015

0021-9193

*Equally contributed to the workIn this paper we report the first crystal structure of a prokaryotic sucrose synthase from the non-photosynthetic bacterium Nitrosomonas europaea . The obtained structure  was in an open form, whereas the only other available structure from the plant Arabidopsis thaliana was in a closed conformation. Comparative structural analysis  revealed a ?hinge-latch? combination, which is critical to transition between the open and closed forms of the enzyme. The N. europaea  sucrose synthase shares the same fold as  the GT-B family of the retaining glycosyltransferases. In addition, a triad of conserved homologous catalytic residues in the family showed to be functionally critical in the N.europaea   sucrose synthase (Arg567, Lys572, Glu663). This implies that sucrose synthase shares not only a common origin with the GT-B family, but also a similar catalytic  mechanism. The enzyme preferred transferring glucose from ADP-glucose rather than  UDP-glucose like the eukaryotic counterparts. This predicts that these prokaryotic  organisms have a different sucrose metabolic scenario from plants. Nucleotide preference  determines where the glucose moiety is targeted after sucrose is degraded.