title: Rossmann-fold motifs can confer multiple functions to metabolic enzymes: RNA binding and ribonuclease activity of a UDP-glucose dehydrogenase.
abstract: Metabolic enzymes are usually characterized to have one specific function, and this is the case of UDP-glucose dehydrogenase that catalyzes the twofold NAD(+)-dependent oxidation of UDP-glucose into UDP-glucuronic acid. We have determined that this enzyme is also capable of participating in other cellular processes. Here, we report that the bacterial UDP-glucose dehydrogenase (UgdG) from Sphingomonas elodea ATCC 31461, which provides UDP-glucuronic acid for the synthesis of the exopolysaccharide gellan, is not only able to bind RNA but also acts as a ribonuclease. The ribonucleolytic activity occurs independently of the presence of NAD(+) and the RNA binding site does not coincide with the NAD(+) binding region. We have also performed the kinetics of interaction between UgdG and RNA. Moreover, computer analysis reveals that the N- and C-terminal domains of UgdG share structural features with ancient mitochondrial ribonucleases named MAR. MARs are present in lower eukaryotic microorganisms, have a Rossmannoid-fold and belong to the isochorismatase superfamily. This observation reinforces that the Rossmann structural motifs found in NAD(+)-dependent dehydrogenases can have a dual function working as a nucleotide cofactor binding domain and as a ribonuclease.
authors.affiliation: Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Barbas
authors.forename: Alma
authors.initials: A
authors.lastname: Popescu
authors.forename: Carlos
authors.initials: C
authors.lastname: Frazão
authors.forename: Cecília M
authors.initials: CM
authors.lastname: Arraiano
authors.forename: Arsénio M
authors.initials: AM
authors.lastname: Fialho
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D012260:Ribonucleases / Q000737:chemistry / Q000378:metabolism*; D020578:Sphingomonas / Q000201:enzymology*; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009243:NAD; D012313:RNA; D014533:Uridine Diphosphate Glucose Dehydrogenase; D012260:Ribonucleases