The closely related yeasts Debaryomyces fabryi and Debaryomyces hansenii are
excellent xylose consumers. We previously described the activity of a highaffinity
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.