4rbn
From Proteopedia
The crystal structure of Nitrosomonas europaea sucrose synthase: Insights into the evolutionary origin of sucrose metabolism in prokaryotes
Structural highlights
FunctionSUS_NITEU Catalyzes the reversible conversion of sucrose and a nucleotide disphosphate (NDP) into fructose and NDP-glucose; although the reaction is freely reversible in vitro, the physiological reaction seems to be sucrose cleavage. Unlike characterized plant enzymes prefers ADP as a cosubstrate, whereas plants prefer UDP (PubMed:25846332, PubMed:26013491). The KM for sucrose is 8-fold lower in the presence of ADP than UDP (PubMed:25846332). Its preference for ADP over UDP suggests it may directly link sucrose and glycogen metabolism (Probable).[1] [2] Publication Abstract from PubMedIn this paper we report the first crystal structure of a prokaryotic sucrose synthase from the nonphotosynthetic 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 was shown to be functionally critical in the N. europaea sucrose synthase (Arg567, Lys572, and 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. IMPORTANCE: We obtained biochemical and structural evidence of sucrose metabolism in nonphotosynthetic bacteria. Until now, only sucrose synthases from photosynthetic organisms have been characterized. Here, we provide the crystal structure of the sucrose synthase from the chemolithoautotroph N. europaea. The structure supported that the enzyme functions with an open/close induced fit mechanism. The enzyme prefers as the substrate adenine-based nucleotides rather than uridine-based like the eukaryotic counterparts, implying a strong connection between sucrose and glycogen metabolism in these bacteria. Mutagenesis data showed that the catalytic mechanism must be conserved not only in sucrose synthases but also in all other retaining GT-B glycosyltransferases. The Crystal Structure of Nitrosomonas europaea Sucrose Synthase Reveals Critical Conformational Changes and Insights into Sucrose Metabolism in Prokaryotes.,Wu R, Asencion Diez MD, Figueroa CM, Machtey M, Iglesias AA, Ballicora MA, Liu D J Bacteriol. 2015 Sep 1;197(17):2734-46. doi: 10.1128/JB.00110-15. Epub 2015 May , 26. PMID:26013491[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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