XYLHencodes a xylose/H⁺symporter from the highly related yeast speciesDebaryomyces fabryiandDebaryomyces hansenii

Abstract

The closely related yeasts Debaryomyces fabryi and Debaryomyces hansenii are excellent xylose consumers. We previously described the activity of a high-affinity xylose/H(+) symport from an industrial strain of D. hansenii subsequently reclassified as D. fabryi. We now report the identification of the gene encoding this permease, AY347871.2. This was retrieved from D. fabryi gDNA using a degenerate primer PCR strategy, based on conserved regions from the amino acid sequences of three well-characterized bacterial xylose/H(+) symporters. This sequence is 86% identical to another, DEHA2C11374p from D. hansenii type strain. DEHA2C11374p was conceptually ascribed to the major facilitator superfamily. The putative amino acid sequence of AY347871.2 and DEHA2C11374p presented a hydrophobicity pattern compatible with plasma membrane proteins. The last was functionally expressed in Saccharomyces cerevisiae. The sensitivity of transport activity to a protonophore confirmed its dependence on proton motive force, as expected from a symporter. We named D. fabryi AY347871.2 and D. hansenii DEHA2C11374p as XYLH from Xylose/H(+) symport. Based on the very high similarity, we suggested that Scheffersomyces stipitis Xut3 and Aspergillus nidulans AN8400.2 may also encode xylose high-affinity permeases.

Identification of a Novel L-rhamnose Uptake Transporter in the Filamentous Fungus Aspergillus niger

“…coli strains (WT and L-rhamnose negative strains) for that purpose, make a comparison difficult. The L-rhamnose uptake rate determined for RhtA was, however, comparable to the maximum sugar uptake rate determined for other fungal MFS transporters, like the D-xylose transporters GXS1 from Candida intermedia [48] or XylH from Debaryomyces hansenii [49]. …”

Organic acid production in Aspergillus niger and other filamentous fungi

“…In this experiment, the L-rhamnose uptake ability of the EBY.VW4000_RhtA strain was determined, using as a negative control the EBY.VW4000 strain expressing the A. niger specific D-xylose transporter XltB (Sloothaak et al, 2016a (Tate et al, 1992), however, the experimental approach used by Tate et al, which performed overnight cultivations of different E. coli strains (WT and L-rhamnose negative strains) for that purpose, make a comparison difficult. The L-rhamnose uptake rate determined for RhtA was, however, comparable to the maximum sugar uptake rate determined for other fungal MFS transporters, like the D-xylose transporters GXS1 from Candida intermedia (Young et al, 2012) or XylH from Debaryomyces hansenii (Ferreira et al, 2013). (1 % w/v) as sole carbon source.…”

The uptake of carbon sources by Aspergillus niger

“…The L-rhamnose uptake rate determined for RhtA is significantly lower than that one reported for the E. coli L-rhamnose transporter [43], however, the experimental approach used by Tate et al, which performed overnight cultivations of different E. coli strains (WT and L-rhamnose negative strains) for that purpose, make a comparison difficult. The L-rhamnose uptake rate determined for RhtA was, however, comparable to the maximum sugar uptake rate determined for other fungal MFS transporters, like the D-xylose transporters GXS1 from Candida intermedia [48] or XylH from Debaryomyces hansenii [49].…”

“…There is some structural variation in this family, because lactose permeases from the Gram-positive bacteria have an additional C-terminal hydrophilic domain that is interacting with the phosphotransferase system like the PTS transporters from superfamily 4.A [48]. Furthermore, indications are found for an ability to form functional homodimers, resulting in a double sugar translocation route [49]. This family, however, does not contribute to the uptake of sugars as substrate for metabolism in fungi.…”

“…HMMxylT was built using the HMMER v3.0 tool [49]. The A. niger ATCC1015 [50] and the T. reesei Rut-C30 [51] proteomes, which were used for the in silico analysis, were downloaded from the JGI database [52].…”