title: Maltose transport in Lactobacillus casei and its regulation by inducer exclusion.
abstract: Transport of maltose in Lactobacillus casei BL23 is subject to regulation by inducer exclusion. The presence of glucose or other rapidly metabolized carbon sources blocks maltose transport by a control mechanism that depends on the phosphorylation of the HPr protein at serine residue 46. We have identified the L. casei gene cluster for maltose/maltodextrin utilization by sequence analysis and mutagenesis. It is composed of genes coding for a transcriptional regulator, oligosaccharide hydrolytic enzymes, an ABC transporter (MalEFGK2) and the enzymes for the metabolism of maltose or the degradation products of maltodextrins: maltose phosphorylase and beta-phospho-glucomutase. These genes are induced by maltose and repressed by the presence of glucose via the catabolite control protein A (CcpA). A mutant strain was constructed which expressed the hprKV267F allele and therefore formed large amounts of P-Ser-HPr even in the absence of a repressive carbon source. In this mutant, transport of maltose was severely impaired, whereas transport of sugars not subject to inducer exclusion was not changed. These results strengthen the idea that P-Ser-HPr controls inducer exclusion and make the maltose system of L. casei a suitable model for studying this process in Firmicutes.
authors: Laboratorio de Bacterias Lácticas y Probióticos, IATA-CSIC, P.O. Box 73, 46100 Burjassot, Valencia, Spain. btcmon@iata.csic.es
authors: Vicente
authors: V
authors: Monedero
authors: María Jesús
authors: MJ
authors: Yebra
authors: Sandrine
authors: S
authors: Poncet
authors: Josef
authors: J
authors: Deutscher
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D015964:Gene Expression Regulation, Bacterial; D007780:Lacticaseibacillus casei / Q000235:genetics / Q000378:metabolism*; D008320:Maltose / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D001426:Bacterial Proteins; D008320:Maltose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr