Abstract: Neurospora crassa has been the model filamentous fungus for the
study of many fundamental cellular mechanisms of transport and metabolism. The
recently completed genome sequence of N. crassa has over 10,000 genes
without significant matches for a large number of genes (41%) in the
sequence databases, indeed presents many challenges for new discoveries. Using
transporter database and BLAST searches a total of 65 open reading frames for
putative cation transporter genes have been identified in N. crassa.
These were further confirmed by characteristic features of the family like
transmembrane domains (TOPPRED 2), conserved motifs (Clustal W) and
phylogenetic analysis (TREETOP). In Neurospora cation transporter genes
constitute nearly 18.3% of the total membrane transport systems, which is
higher than E. coli (8.8%), S. cerevisiae (13.7%), S.
pombe (17.2%), A. fumigatus (10.1%), A. thaliana (16.8%)
and H. sapiens (15.6%). We refer to the complete complement of metal
ion transporter genes as "Metal Transportome". There are a total of 33
putative transporters for alkali and alkaline earth metals constituting 18 for
calcium (P-ATPase, VIC, CaCA, Mid1), 7 for sodium (P-ATPase, CPA1, CPA2), 4 for
potassium (Trk, VIC, KUP), and 4 for magnesium (MIT). Transition metal ion
transporters account for 32 transporters including 7 for zinc (ZIP), 6 for
copper (Ctr2, Ctr1), 2 each for manganese (Nramp), iron (OFeT), arsenite
(ArsAB, ACR3) and other metal ions (ABC and P-ATPase) and 1 each for nickel
(NiCoT) and chromate (CHR). N. crassa has 7 linkage groups of which LGI
harbors 21 of metal ion transporters and in contrast LGVII has only 2. Studies
on metal transportomes of different organisms will help to unravel the role of
metal ion transporters in homeostasis.
Keywords: Metal ion transporters, transportome, metals, transporters, Neurospora crassa
