A gene encoding a putative membrane protein homologous to the major facilitator superfamily of transporters maps upstream of the beta-glycosidase gene in the archaeon Sulfolobus solfataricus.

We have identified a gene encoding a putative membrane protein homologous to the major facilitator superfamily, mapping upstream of the lacS gene in Sulfolobus solfataricus. Permeases from this family mediate secondary transport and are widely distributed among eubacteria and eukaryotes; the finding of an archaeal member suggests that this mechanism of transport evolved before the divergence of the three living domains. We also report a transcriptional mapping of the gene cluster.