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)

Research output: Contribution to journalArticleScientificpeer-review

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 Sep 2021
MoE publication typeA1 Journal article-refereed

Keywords

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

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