title: Cloning and biochemical analysis of β-glucoside utilization (bgl) operon without phosphotransferase system in Pectobacterium carotovorum subsp. carotovorum LY34.
abstract: β-Glucosidases are widespread in bacteria and involved in the metabolism of various carbohydrate substrates. Studying of β-glucoside utilization (bgl) operons on operon of Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34) will help us understanding how β-glucoside utilization (bgl) operon can cooperate with other systems in bacterium caused soft-rot disease. Pcc LY34 causes soft-rot disease in plants and expresses multiple enzymatic forms of β-glucosidases. To fully explore the β-glucoside utilization system in Pcc LY34, we have isolated a bgl operon from a genomic library for screening of β-glucosidase activities. Sequence analysis of a 3050bp cloned DNA fragment (accession number AY870655) shows two open reading frames (bglY and bglK) that are predicted to encode proteins of 474 and 278 amino acid residues, respectively. Pair wise similarity analysis suggests BglY is a beta-glucosidase (a member of glycosyl hydrolase family 1) and BglK is a transcriptional antiterminator protein. bglY promoter region contains an inverted repeat sequence similar to transcriptional terminator. Different from other four β-glucoside utilization operons of Pcc LY34 strain, BglY contains signal peptide sequences as extracellular β-glucosidase. Comparisons of five β-glucoside utilization operons of Pcc LY34 strain showed that bglYK operon does not have phosphotransferase system domain which are responsible for sugar transportation. BglY shares 33-44% identity with other four β-glucosidases of Pcc LY34 strain. Enzyme assay showed that purified BglY enzyme hydrolyzed salicin, arbutin, pNPG, and MUG, and exhibited maximal activity at pH 7.0 and 40°C. This activity was enhanced Mg(2+). Site-directed mutagenesis revealed E166 and E371 are critical of BglY's β-glucosidase activity.
authors.affiliation: Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, NV, United States.
authors.forename: Chang Long
authors.initials: CL
authors.lastname: An
authors.forename: Min Keun
authors.initials: MK
authors.lastname: Kim
authors.forename: Tae Ho
authors.initials: TH
authors.lastname: Kang
authors.forename: Jungho
authors.initials: J
authors.lastname: Kim
authors.forename: Hoon
authors.initials: H
authors.lastname: Kim
authors.forename: Han Dae
authors.initials: HD
authors.lastname: Yun
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005960:Glucosides / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009876:Operon; D016973:Pectobacterium carotovorum / Q000235:genetics* / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D004269:DNA, Bacterial; D005960:Glucosides