Rhizobium leguminosarum bv. trifolii mutants unable to catabolize the methyl-pentose rhamnose are unable to compete effectively for nodule occupancy. In this work we show that the locus responsible for the transport and catabolism of rhamnose spans 10,959 bp. Mutations in this region were generated by transposon mutagenesis, and representative mutants were characterized. The locus contains genes coding for an ABC-type transporter, a putative dehydrogenase, a probable isomerase, and a sugar kinase necessary for the transport and subsequent catabolism of rhamnose. The regulation of these genes, which are inducible by rhamnose, is carried out in part by a DeoR-type negative regulator (RhaR) that is encoded within the same transcript as the ABC-type transporter but is separated from the structural genes encoding the transporter by a terminator-like sequence. RNA dot blot analysis demonstrated that this terminator-like sequence is correlated with transcript attenuation only under noninducing conditions. Transport assays utilizing tritiated rhamnose demonstrated that uptake of rhamnose was inducible and dependent upon the presence of the ABC transporter at this locus. Phenotypic analyses of representative mutants from this locus provide genetic evidence that the catabolism of rhamnose differs from previously described methyl-pentose catabolic pathways.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC532407 | PMC |
| http://dx.doi.org/10.1128/JB.186.24.8433-8442.2004 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Structure and mechanism of biosynthesis of Streptococcus mutans cell wall polysaccharide.
Nat Commun
January 2025
Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA.
Streptococcus mutans, the causative agent of human dental caries, expresses a cell wall attached Serotype c-specific Carbohydrate (SCC) that is critical for cell viability. SCC consists of a polyrhamnose backbone of →3)α-Rha(1 → 2)α-Rha(1→ repeats with glucose (Glc) side-chains and glycerol phosphate (GroP) decorations. This study reveals that SCC has one predominant and two more minor Glc modifications.
View Article and Find Full Text PDFMultiple Enzymes Expressed by the Gut Microbiota Can Transform Typhaneoside and Are Associated with Improving Hyperlipidemia.
Adv Sci (Weinh)
January 2025
State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences/Peking Union Medical College, Beijing, 100050, China.
The mechanism of multiple enzymes mediated drug metabolism in gut microbiota is still unclear. This study explores multiple enzyme interaction process of typhactyloside (TYP) with gut microbiota and its lipid-lowering pharmacological activity. TYP, with bioavailability of only 2.
View Article and Find Full Text PDFCoexpression of D-Allulose 3-Epimerase and L-Rhamnose Isomerase in through a Dual Promoter Enables High-Level Biosynthesis of D-Allose from D-Fructose in One Pot.
J Agric Food Chem
January 2025
School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, PR China.
D-Allose, a rare sugar, has gained significant attention not only as a low-calorie sweetener but also for its anticancer, antitumor, anti-inflammatory, antioxidant, and other pharmaceutical properties. Despite its potential, achieving high-level biosynthesis of D-allose remains challenging due to inefficient biocatalysts, low conversion rates, and the high cost of substrates. Here, we explored the food-grade coexpression of D-allulose 3-epimerase (Bp-DAE) and L-rhamnose isomerase (BsL-RI) within a single cell using WB800N as the host.
View Article and Find Full Text PDFDifferences in utilization and metabolism of Ulva lactuca polysaccharide by human gut Bacteroides species in the in vitro fermentation.
Carbohydr Polym
March 2025
Shenzhen Key Laboratory of Food Nutrition and Health, College of Chemistry and Environmental Engineering, GuangDong Engineering Technology Research Center of Aquatic Food Processing and Safety Control, Institute for Innovative Development of Food Industry, Shenzhen University, Shenzhen 518060, China; National Engineering Research Center of Seafood, National & Local Joint Engineering Laboratory for Marine Bioactive Polysaccharide Development and Application, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, China. Electronic address:
Ulva lactuca polysaccharide (ULP), a sulfated polysaccharide, has been widely used in Asia. However, its digestion process and utilization by gut microbiota remain poorly understood. In this study, the in vitro simulated digestion and fermentation were used to analyze the digestibility of ULP.
View Article and Find Full Text PDFSurface display and characterization of recombinant α-l-Rhamnosidase from Emiliania huxleyi on Pichia pastoris.
Bioorg Chem
February 2025
Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China; Key Laboratory of Green Processing and Intelligent Manufacturing of Lingnan Specialty Food, Ministry of Agriculture, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
An α-l-Rhamnosidase gene with an open reading frame of 3192 bp encoding a 1036-amino acid protein (EhRha) was cloned from Emiliania huxleyi for flavonoid hydrolysis on the cell surface of Pichia pastoris (P. pastoris) strain GS115 by fusing with the anchor protein (AGα1) from Saccharomyces cerevisiae. Fluorescence microscopy and flow cytometry assays revealed that EhRha was successfully displayed on the cell surface of P.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!