Functional characterization of a highly specific l-arabinose transporter from Trichoderma reesei

Sami Havukainen, Jonai Pujol-Giménez, Mari Valkonen, Matthias A. Hediger, Christopher P. Landowski*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)
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Abstract

Background: Lignocellulose biomass has been investigated as a feedstock for second generation biofuels and other value-added products. Some of the processes for biofuel production utilize cellulases and hemicellulases to convert the lignocellulosic biomass into a range of soluble sugars before fermentation with microorganisms such as yeast Saccharomyces cerevisiae. One of these sugars is l-arabinose, which cannot be utilized naturally by yeast. The first step in l-arabinose catabolism is its transport into the cells, and yeast lacks a specific transporter, which could perform this task.

Results: We identified Trire2_104072 of Trichoderma reesei as a potential l-arabinose transporter based on its expression profile. This transporter was described already in 2007 as d-xylose transporter XLT1. Electrophysiology experiments with Xenopus laevis oocytes and heterologous expression in yeast revealed that Trire2_104072 is a high-affinity l-arabinose symporter with a Km value in the range of ∼ 0.1–0.2 mM. It can also transport d-xylose but with low affinity (Km∼ 9 mM). In yeast, l-arabinose transport was inhibited slightly by d-xylose but not by d-glucose in an assay with fivefold excess of the inhibiting sugar. Comparison with known l-arabinose transporters revealed that the expression of Trire2_104072 enabled yeast to uptake l-arabinose at the highest rate in conditions with low extracellular l-arabinose concentration. Despite the high specificity of Trire2_104072 for l-arabinose, the growth of its T. reesei deletion mutant was only affected at low l-arabinose concentrations.

Conclusions: Due to its high affinity for l-arabinose and low inhibition by d-glucose or d-xylose, Trire2_104072 could serve as a good candidate for improving the existing pentose-utilizing yeast strains. The discovery of a highly specific l-arabinose transporter also adds to our knowledge of the primary metabolism of T. reesei. The phenotype of the deletion strain suggests the involvement of other transporters in l-arabinose transport in this species.

Original languageEnglish
Article number177
JournalMicrobial Cell Factories
Volume20
DOIs
Publication statusPublished - 8 Sept 2021
MoE publication typeA1 Journal article-refereed

Funding

The work was funded by Academy of Finland (funding decision No. 298392). Prof. Matthias Hediger acknowledges the support of the electrophysiology studies by the Swiss National Science Foundation Grant Sinergia #CRSII5 180326.

Keywords

  • Arabinose transporter
  • Pentose fermentation
  • Transmembrane transport
  • Trichoderma reesei

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