Molecular Analysis of the xylFGH Operon, Coding for Xylose ABC Transport, in Thermoanaerobacter ethanolicus

Abstract

A xylose ABC (ATP-binding cassette) transport operon, xylFGH, was cloned from Thermoanaerobacter ethanolicus, a thermophilic ethanol-producing eubacterium. The cistrons code for a periplasmic D-xylose-binding protein (XylF, partial sequence of 250 amino acids), ATP-binding protein (XylG, 505 amino acids), and integral membrane protein (XylH, 388 amino acids). These results, together with previous work, indicate that duplicate copies of both xylF and xylH are present in the T. ethanolicus chromosome, suggesting ancient gene duplication or lateral gene transfer events. XylG resembles other eubacterial monosaccharide ABC-ATPases in that its two nucleotide-binding domains (NBDs) are highly homologous, yet significantly different with respect to putative catalytic residues. Unlike most other integral membrane ABC transport proteins, XylH apparently contains 11 or 12 transmembrane segments (TMS) and is similar to a small group of ABC permeases that defy the "2 x 6" helix paradigm. This is the first report of a monosaccharide ABC transport operon in a thermophilic anaerobic eubacterium.

A Member of the Second Carbohydrate Uptake Subfamily of ATP-Binding Cassette Transporters Is Responsible for Ribonucleoside Uptake inStreptococcus mutans

“…Other members of the CUT2 subfamily of ABC transporters are known to transport monosaccharides (such as ribose [3], galactose [24], xylose [6], and rhamnose [23]), the autoinducer AI2 (29,30), and erythritol (33). As ribonucleoside uptake has not been previously demonstrated in this group, or by any other ABC permease, this report extends the range of substrates known to be transported by ABC transporters.…”

“…One of the three putative carbohydrate ABC transporters in S. mutans is a member of the second carbohydrate uptake transporter (CUT2) subfamily. In other species of bacteria, members of this subfamily are involved in the uptake of monosaccharides such as ribose (3) and xylose (6). However, the genetic context of the genes encoding the CUT2 transporter in S. mutans ( Fig.…”

The metagenome of a biogas-producing microbial community of a production-scale biogas plant fermenter analysed by the 454-pyrosequencing technology

“…Likewise, other species identified by BLAST analysis of contig sequences potentially are cabable of producing metabolites that indirectly or directly contribute to biogas formation from plant material. Pelotomaculum thermopropionicum (Kosaka et al, 2008), Thermoanaerobacter ethanolicus (Erbeznik et al, 2004) and Victivallis vadensis, originally isolated from human faeces (Zoetendal et al, 2003), should be mentioned in this context.…”

Thermoanaerobacterthermohydrosulfuricus WC1 Shows Protein Complement Stability during Fermentation of Key Lignocellulose-Derived Substrates

“…(17,20,67,68), and would consume 1 mol of ATP per mol of xylose transported. Conversely, transport of the disaccharide cellobiose seemingly occurs via PTS-mediated mechanisms.…”