RECENT ADVANCES IN THE MOLECULAR-BIOLOGY OF A FAMILY OF EUKARYOTIC HIGH-AFFINITY NITRATE TRANSPORTERS

Nitrate transporters have now been cloned from bacteria, fungi, algae and higher plants, and those identified to date belong to three distin ct transporter superfamilies: the ABC (ATP-binding cassette) superfami ly, the POT (proton-dependent oligopeptide transporter) superfamily an d the MFS (major facilitator superfamily). The crnA gene from the fung us Aspergillus nidulans and the nar-3/nar-4 genes from the green alga Chlamydomonas reinhardtii encode high affinity NO3- transporters belon ging to the MFS, and recently homologues of crnA have also been identi fied in higher plants. In this paper we review our current state of kn owledge regarding the structure, evolutionary relationships and regula tion of the crnA family of NO3- transport proteins.