title: Transcriptional analysis of levU operon encoding saccharolytic enzymes and two apparent genes involved in amino acid biosynthesis in Zymomonas mobilis.
abstract: Extracellular levansucrase (LevU) and sucrase (InvB) are two of the three saccharolytic enzymes involved in the sucrose metabolism of Zymomonas mobilis. The levU and invB genes were clustered with a 155bp interval on the chromosome. Both genes were transcribed constitutively at the basal level and the transcription of both genes was induced significantly when sucrose was added to the medium. These genes were transcribed as a bicistronic mRNA and the expression was modulated by a single promoter, which is located upstream of the levU gene. The transcriptional initiation site was mapped to -64bp from the translation start site of levU gene. These results indicated that two genes are most likely to constitute an operon. The glk operon, which encodes four glycolytic enzymes, was located close to the levU operon on the chromosome. Two apparent ORFs (ORF3 and 4) were found at the intervening sequence located between the glk and levU operons. These ORFs were transcribed divergently and showed high homology at the amino acid level with the bacterial global regulatory protein (Lrp) and aspartate racemase.
authors.affiliation: Microbial Metabolic Engineering Research Unit, Korea Research Institute of Bioscience and Biotechnology (KRIBB), PO Box 115, Yusong, Taejon 305-600, South Korea.
authors.forename: K B
authors.initials: KB
authors.lastname: Song
authors.forename: J W
authors.initials: JW
authors.lastname: Seo
authors.forename: S K
authors.initials: SK
authors.lastname: Rhee
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000096:biosynthesis*; D001483:Base Sequence; D015152:Blotting, Northern; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006019:Glycolysis; D006602:Hexosyltransferases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D018085:Regulon / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013393:Sucrase / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D017355:Zymomonas / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D006602:Hexosyltransferases; C021513:levansucrase; D013393:Sucrase; D000591:Amino Acid Isomerases; C019749:aspartate racemase