Maltose transport in Lactobacillus casei and its regulation by inducer exclusion

• Published in: Research in microbiology Vol. 159; no. 2; pp. 94 - 102
• Main Authors: Monedero, Vicente, Yebra, María Jesús, Poncet, Sandrine, Deutscher, Josef
• Format: Journal Article
• Language: English
• Published: Paris Elsevier Masson SAS 01.03.2008; Elsevier
• Subjects: ABC transporter; Bacterial Proteins; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biochemistry, Molecular Biology; Biological and medical sciences; Biological Transport; Carbohydrate Metabolism; Firmicutes; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Inducer exclusion; Lactobacillus casei; Lactobacillus casei - genetics; Lactobacillus casei - metabolism; Life Sciences; Maltose; Maltose - metabolism; Microbiology; Miscellaneous; Molecular biology; Molecular Sequence Data; Mutagenesis; Operon; P-Ser-HPr; Phosphoenolpyruvate Sugar Phosphotransferase System; Phosphoenolpyruvate Sugar Phosphotransferase System - genetics; Phosphoenolpyruvate Sugar Phosphotransferase System - metabolism; Phosphorylation; P-Ser-HPr; Maltose; Lactobacillus casei; ABC transporter; Inducer exclusion; Lactic acid bacteria; Bacteria; Lactobacillaceae; Lactobacillus; Phosphoenolpyruvate Sugar Phosphotransferase System; Phosphorylation
• ISSN: 0923-2508; 1769-7123; 0923-2508
• DOI: 10.1016/j.resmic.2007.10.002

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 β-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.