title: Requirement of the Lactobacillus casei MaeKR two-component system for L-malic acid utilization via a malic enzyme pathway.
abstract: Lactobacillus casei can metabolize L-malic acid via malolactic enzyme (malolactic fermentation [MLF]) or malic enzyme (ME). Whereas utilization of L-malic acid via MLF does not support growth, the ME pathway enables L. casei to grow on L-malic acid. In this work, we have identified in the genomes of L. casei strains BL23 and ATCC 334 a cluster consisting of two diverging operons, maePE and maeKR, encoding a putative malate transporter (maeP), an ME (maeE), and a two-component (TC) system belonging to the citrate family (maeK and maeR). Homologous clusters were identified in Enterococcus faecalis, Streptococcus agalactiae, Streptococcus pyogenes, and Streptococcus uberis. Our results show that ME is essential for L-malic acid utilization in L. casei. Furthermore, deletion of either the gene encoding the histidine kinase or the response regulator of the TC system resulted in the loss of the ability to grow on L-malic acid, thus indicating that the cognate TC system regulates and is essential for the expression of ME. Transcriptional analyses showed that expression of maeE is induced in the presence of L-malic acid and repressed by glucose, whereas TC system expression was induced by L-malic acid and was not repressed by glucose. DNase I footprinting analysis showed that MaeR binds specifically to a set of direct repeats [5'-TTATT(A/T)AA-3'] in the mae promoter region. The location of the repeats strongly suggests that MaeR activates the expression of the diverging operons maePE and maeKR where the first one is also subjected to carbon catabolite repression.
authors.affiliation: Departamento de Biotecnología de Alimentos, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), P.O. Box 73, 46100 Burjassot, Valencia, Spain.
authors.forename: José María
authors.initials: JM
authors.lastname: Landete
authors.forename: Luisa
authors.initials: L
authors.lastname: García-Haro
authors.forename: Amalia
authors.initials: A
authors.lastname: Blasco
authors.forename: Paloma
authors.initials: P
authors.lastname: Manzanares
authors.forename: Carmen
authors.initials: C
authors.lastname: Berbegal
authors.forename: Vicente
authors.initials: V
authors.lastname: Monedero
authors.forename: Manuel
authors.initials: M
authors.lastname: Zúñiga
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D013293:Enterococcus faecalis / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D000071677:Histidine Kinase; D007780:Lacticaseibacillus casei / Q000235:genetics* / Q000378:metabolism*; D008293:Malates / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D005810:Multigene Family; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013291:Streptococcus / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008293:Malates; D014157:Transcription Factors; C030298:malic acid; D011494:Protein Kinases; D000071677:Histidine Kinase