Sulfolobus acidocaldarius Transports Pentoses via a Carbohydrate Uptake Transporter 2 (CUT2)-Type ABC Transporter and Metabolizes Them through the Aldolase-Independent Weimberg Pathway

Abstract

possess a great metabolic versatility and grow heterotrophically on various carbon sources such as different sugars and peptides. Known sugar transporters in Archaea predominantly belong to ABC transport systems. Although several ABC transporters for sugar uptake have been characterized in the crenarchaeon , only one homologue of these transporters, the maltose/maltooligomer transporter, could be identified in the closely related Comparison of the transcriptome of grown on peptides alone and peptides in presence of D-xylose allowed for the identification of the ABC transporter for D-xylose and L-arabinose transport and to gain deeper insights into pentose catabolism under the respective growth conditions. The D-xylose/L-arabinose substrate binding protein (SBP) (Saci_2122) of the ABC transporter is unique in Archaea and shares more similarity to bacterial SBPs of the Carbohydrate Uptake Transporter-2 (CUT2) family than to any characterized archaeal one. The identified pentose transporter is the first CUT2 family ABC transporter analyzed in the domain of Archaea. Single gene deletion mutants of the ABC transporter subunits exemplified the importance of the transport system for D-xylose and L-arabinose uptake. Next to the transporter operon, enzymes of the aldolase-independent pentose catabolism branch were found to be upregulated in N-Z-Amine and D-xylose medium. The α-ketoglutarate semialdehyde dehydrogenase (KGSADH; Saci_1938) seemed not to be essential for growth on pentoses. However, the deletion mutant of the 2-keto-3-deoxyarabinoate/xylonate dehydratase (KDXD/KDAD; Saci_1939) was no longer able to catabolize D-xylose or L-arabinose suggesting the absence of the aldolase-dependent branch in Thermoacidophilic microorganisms are emerging model organisms for biotechnological applications as their optimal growth conditions resemble conditions used in certain biotechnologies such as plant waste industrial degradation. Because of its high genome stability is especially suited as a platform organism for such applications. For the use in (ligno)cellulose degradation, it was important to understand the pentose uptake and metabolism in This study revealed that only the aldolase-independent Weimberg pathway is required for growth of on D-xylose and L-arabinose. Moreover, employs a CUT2 ABC transporter for pentose uptake, which is more similar to bacterial than to archaeal ABC transporters. The identification of pentose inducible promoters will expedite the metabolic engineering of for its development into a platform organism for (ligno)cellulose degradation.

Biochemical routes for uptake and conversion of xylose by microorganisms

“…It is revealed that this pentose transporter is the first identified ABC transporter of the carbohydrate uptake transporter-2 (CUT2) family in the domain of Archaea. In addition, the growth defect on d-xylose in the single-gene deletion mutants of ABC transporter further illustrated the importance of this transport system [22]. Sulfolobus solfataricus and the closely related Sulfolobus acidocaldarius are the best-studied organisms in the phylum of crenarchaeota for sugar transport, and a number of sugar ABC transporters have been identified and examined [23,24].…”

“…Sulfolobus solfataricus and the closely related Sulfolobus acidocaldarius are the best-studied organisms in the phylum of crenarchaeota for sugar transport, and a number of sugar ABC transporters have been identified and examined [23,24]. Besides those ABC transporters, only the MFS transporter for glucose and PTS system for d-fructose were characterized in Haloferax volcanii and Haloarchaea, respectively [22].…”

A combined experimental and modelling approach for the Weimberg pathway optimisation

“…1a) has gained major attention 8 . The pathway has been identified in several bacteria and archaea [9][10][11][12] , and is best understood for the oligotrophic freshwater bacterium Caulobacter crescentus, in which the involved enzymes are encoded in the D-xylose-inducible xylXABCD operon (CC0823-CC0819) 13 (Fig. 1b).…”

Structural insights into the catalytic and substrate recognition mechanisms of bacterial l‐arabinose 1‐dehydrogenase

“…Although the first and second metabolic pathways are phosphorylative pathways, the third pathway, found in bacteria and archaea, is partially equivalent to the nonphosphorylative Entner-Doudoroff pathway [5]. metabolism, in which L-KDP is converted to pyruvate and glycolaldehyde (Route I) [6,7], a-ketoglutarate (Route II) [8][9][10][11], or pyruvate and glycolate (Route III) [12]. L-Arabino-c-lactone is then converted to L-2-keto-3deoxypentonate (L-KDP) by L-arabinonolactonase (EC 3.1.1.15) and L-arabonate dehydratase (EC 4.2.1.25).…”

“…metabolism, in which L-KDP is converted to pyruvate and glycolaldehyde (Route I) [6,7], a-ketoglutarate (Route II) [8][9][10][11], or pyruvate and glycolate (Route III) [12].…”