Transcriptional Regulation and Signal-Peptide-Dependent Secretion of Exolevanase (LsdB) in the Endophyte Gluconacetobacter diazotrophicus

• Published in: Applied and Environmental Microbiology Vol. 75; no. 6; pp. 1782 - 1785
• Main Authors: Menéndez, Carmen, Banguela, Alexander, Caballero-Mellado, Jesús, Hernández, Lázaro
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.03.2009; American Society for Microbiology (ASM)
• Subjects: Amino Acid Sequence; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Base Sequence; Biological and medical sciences; Endophytes; Fructans - metabolism; Fructose - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Order; Genes; Gluconacetobacter - enzymology; Gluconacetobacter - genetics; Gluconacetobacter diazotrophicus; Glucose; Glucose - metabolism; Glycoside Hydrolases - biosynthesis; Glycoside Hydrolases - genetics; Microbiology; Molecular Sequence Data; Mutation; Operon; Organisms; Peptides; Periplasm - enzymology; Plant Microbiology; Protein Sorting Signals; Reverse Transcriptase Polymerase Chain Reaction; Transcription, Genetic; Acetobacteraceae; Gluconacetobacter diazotrophicus; Leader peptide; Regulation(control); Transcription; Secretion; Bacteria; Endophyte
• ISSN: 0099-2240; 1098-5336; 1098-6596
• DOI: 10.1128/AEM.01887-08

Gluconacetobacter diazotrophicus utilizes plant sucrose with a constitutively expressed levansucrase (LsdA), producing extracellular levan, which may be degraded under energetically unfavored conditions. Reverse transcriptase-PCR analysis revealed that lsdA and the downstream exolevanase gene (lsdB) form an operon. lsdB transcription was induced during growth with low fructose concentrations (0.44 to 33 mM) and repressed by glucose. Transport of LsdB to the periplasm involved N-terminal signal peptide cleavage. Type II secretion mutants failed to transfer LsdB across the outer membrane, impeding levan hydrolysis.