title: The signal peptide sequence of a lytic transglycosylase of Neisseria meningitidis is involved in regulation of gene expression.
abstract: The 60 nucleotides encoding the signal peptide of the Neisseria meningitidis membrane-bound lytic transglycosylase (MltA) homologue GNA33 were found to exert a negative regulatory effect on expression of GNA33 from either a T7- or a P(lac)-driven system in Escherichia coli. Down-regulation was observed to occur at the transcriptional/post-transcriptional level and could possibly be ascribed to the formation of a stem-loop secondary structure within the signal peptide sequence. Slowing down the transcription rate through inhibition/titration of the RNA polymerase resulted in a considerable increase in mRNA accumulation, suggesting that a better coupling of translation to transcription would impede the formation of the putative secondary structure. Screening of synonymous mutations in the signal peptide sequence that showed high-level expression of an in-frame fusion to a reporter resulted in the isolation of several deletion mutants lacking most of the sequence participating in the putative secondary structure. Interestingly, the increase in the steady-state mRNA level observed in deletion mutants was higher, reaching a 300-fold increment, than that found in substitution mutants. Our results support the hypothesis that the rate of transcription controls the formation of a secondary structure in the region of the GNA33 transcript corresponding to the signal peptide sequence and this, when formed, negatively regulates expression.
authors.affiliation: IRIS, Chiron S.r.l., Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Serruto
authors.affiliation: IRIS, Chiron S.r.l., Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: Cesira L
authors.initials: CL
authors.lastname: Galeotti
mesh_terms: D001483:Base Sequence; D015536:Down-Regulation; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D016695:Glycosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000201:enzymology* / Q000235:genetics; D017354:Point Mutation; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D021382:Protein Sorting Signals; D016695:Glycosyltransferases; C021815:murein transglycosylase