MFS transportome of the human pathogenic yeast Candida albicans

Abstract

Background: The major facilitator superfamily (MFS) is one of the two largest superfamilies of membrane transporters present ubiquitously in bacteria, archaea, and eukarya and includes members that function as uniporters, symporters or antiporters. We report here the complete transportome of MFS proteins of a human pathogenic yeast Candida albicans.

Results: Computational analysis of C. albicans genome enabled us to identify 95 potential MFS proteins which clustered into 17 families using Saier's Transport Commission (TC) system. Among these SP, DHA1, DHA2 and ACS represented major families consisting of 22, 22, 9 and 16 members, respectively. Family designations in C. albicans were validated by subjecting Saccharomyces cerevisiae genome to TC system. Based on the published available genomics/proteomics data, 87 of the putative MFS genes of C. albicans were found to express either at mRNA or protein levels. We checked the expression of the remaining 8 genes by using RT-PCR and observed that they are not expressed under basal growth conditions implying that either these 8 genes are expressed under specific growth conditions or they may be candidates for pseudogenes.

Conclusion: The in silico characterisation of MFS transporters in Candida albicans genome revealed a large complement of MFS transporters with most of them showing expression. Considering the clinical relevance of C. albicans and role of MFS members in antifungal resistance and nutrient transport, this analysis would pave way for identifying their physiological relevance.

Figure 1

Predicted topology of putative MFS proteins of C. albicans. The topology of the putative MFS proteins was predicted using TMHMM program . The transmembrane domains were found to be either 12 or 14 transmembrane spanners.

Figure 2

Expression analysis of putative MFS genes by RT-PCR. The expression of 8 putative MFS genes, which were not validated by the mRNA/protein profiling data mining, was checked by RT-PCR. Purified poly(A)⁺ enriched mRNA fractionated from C. albicans isolate SC5314 were amplified by RT-PCR, as described in the Methods. Following electrophoresis through 1.2% agarose gel, the amplified PCR products were visualized by staining with ethidium bromide. Lane M, nucleotide size marker (PCR Marker); lane 1, without RT (negative control); lane 2, MDR1 (positive control, 330 base pairs); lane 3, orf19.1582; lane 4, orf19.7336; lane 5, orf19.4090; lane 6, orf19.6180; lane 7, orf19.1424; lane 8, orf19.6520; lane 9, orf19.6654 and lane 10, orf19.6976.

Figure 3

Distribution of MFS families in C. albicans as per transport commission (TC) system and comparison with S. cerevisiae. (A) Family designations were according to TC system as mentioned in the Methods. Ca and Sc stand for C. albicans and S. cerevisiae, respectively. Out of 61 reported MFS families in TC database , 17 were identified in C. albicans as compared to 12 known in S. cerevisiae. (B) A comparison of MFS families between C. albicans and S. cerevisiae revealed that the members of the same family were almost equal in number in both the yeasts. Interestingly, 6 families that were present in C. albicans had no representation in S. cerevisiae whereas there was only one such family in S. cerevisiae which had no counterpart in C. albicans.