title: Repressible cation-phosphate symporters in Neurospora crassa.
abstract: The filamentous fungus Neurospora crassa possesses two nonhomologous high-affinity phosphate permeases, PHO-4 and PHO-5. We have isolated separate null mutants of these permeases, allowing us to study the remaining active transporter in vivo in terms of phosphate uptake and sensitivity to inhibitors. The specificity for the cotransported cation differs for PHO-4 and PHO-5, suggesting that these permeases employ different mechanisms for phosphate translocation. Phosphate uptake by PHO-4 is stimulated 85-fold by the addition of Na+, which supports the idea that PHO-4 is a Na(+)-phosphate symporter. PHO-5 is unaffected by Na+ concentration but is much more sensitive to elevated pH than is PHO-4. Presumably, PHO-5 is a H(+)-phosphate symporter. Na(+)-coupled symport is usually associated with animal cells. The finding of such a system in a filamentous fungus is in harmony with the idea that the fungal and animal kingdoms are more closely related to each other than either is to the plant kingdom.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison 53706, USA.
authors.forename: W K
authors.initials: WK
authors.lastname: Versaw
authors.forename: R L
authors.initials: RL
authors.lastname: Metzenberg
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D004268:DNA-Binding Proteins; D004794:Enzyme Repression; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009492:Neurospora crassa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D028061:Phosphate Transport Proteins; D010710:Phosphates / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D029701:Saccharomyces cerevisiae Proteins; D012965:Sodium Chloride / Q000494:pharmacology; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; C060292:PHO4 protein, S cerevisiae; D028061:Phosphate Transport Proteins; D010710:Phosphates; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012965:Sodium Chloride; C055831:phosphate permease; D011189:Potassium Chloride; D008094:Lithium