XYLH encodes a xylose/H+ symporter from the highly related yeast species Debaryomyces fabryi and Debaryomyces hansenii

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.