Identification and Phylogenetic Analysis of a Glucose Transporter Gene Family from the Human Pathogenic Yeast Candida albicans

We have identified a large family of glucose transporter genes (HGT1 to HGT20) from the human pathogenic yeast Candida albicans by screening of genomic sequences, reverse-transcription PCR assays, and phylogenetic analyses. The putative glucose transporter ORF sequences share among themselves 10–93% pairwise sequence identity and, in comparative analyses of predicted amino acid sequences, exhibit similarities to human and yeast transporters of the major facilitator superfamily (MFS): the predicted 12-transmembrane domains and sugar transporter signatures align closely to those of HXT transporters of Saccharomyces cerevisiae and GLUT transporters of humans, with amino acid residues at certain positions highly conserved throughout the families. Reverse-transcription PCR analyses demonstrated that the majority of the glucose transporters was transcribed in culture medium containing 2% glucose, while several were transcribed in the presence of low (0.2%) and/or high (5%) concentrations of glucose. Phylogenetic analyses revealed that there were three distinct clades of 20 HGT genes, which might represent three possible subfamilies. Additionally, HGT18 and HGT20 show a high overall sequence identity to the human GLUTs, indicating a possible functional convergence. We conclude that glucose transporters in C. albicans comprise a family of 20 known members, with variable transcription in response to glucose concentration.