NCU01540: biological evidence

NCU01540 is a predicted SPX-regulated phosphate transporter of the fungal Pho87/Pho90/Pho91 group. Its SPX regulatory domain and multi-pass permease region support phosphate transport and phosphate/polyphosphate homeostasis. The Pho91 subfamily assignment favors a role in intracellular phosphate handling, but its resident membrane, transport direction, and coupling ion in Neurospora crassa remain unresolved.

• phosphate transmembrane transporter activity: The SPX plus CitMHS permease architecture and Pho91 subfamily assignment support phosphate transport by transfer from experimentally characterized fungal Pho87/Pho90/Pho91 transporters. This supports the curated phosphate-transport IBA without specifying coupling or direction.
• plasma membrane: The IBA derives from PTN000031793 in a broad transporter family. Pho87/Pho90 operate at the plasma membrane whereas the characterized Pho91 is vacuolar, and the target is classified in a Pho91 subfamily. The available evidence does not resolve whether the ancestral plasma-membrane assertion applies to this filamentous-fungal branch; neither location is treated as experimentally established for NCU01540.
• polyphosphate metabolic process: The characterized yeast Pho91 transporter changes vacuolar polyphosphate accumulation through phosphate handling. This supports a conserved indirect contribution to polyphosphate metabolism, not intrinsic polyphosphate synthesis or hydrolysis.
• phosphate ion transport: Phosphate movement is the conserved process of the supported Pho91-like transporter family; the target subfamily assignment and yeast transporter experiments ground this inference.
• membrane: The membrane location is supported by the multi-pass permease architecture independently of whether the resident membrane is plasma or vacuolar.
• transmembrane transporter activity: The supported Pho91 subfamily and characterized fungal phosphate transport justify phosphate transmembrane transporter activity rather than an unspecified solute.
• transmembrane transport: The phosphate substrate is supported by the SPX-Pho91 family assignment and primary characterization of its fungal relatives; phosphate ion transport is the more precise process.

Primary evidence excerpts

• [file:NEUCR/NCU01540/NCU01540-uniprot.txt] “DR PANTHER; PTHR10283:SF92; LOW-AFFINITY PHOSPHATE TRANSPORTER PHO91; 1.”
• PMID:17804816 “the low-affinity transporter Pho91 limits poly P accumulation in a strain
  lacking PHO85. This phenotype was not caused by a regulatory effect on the PHO
  pathway, but can be attributed to the unexpected localization of Pho91 in the
  vacuolar membrane.”
• [file:NEUCR/NCU01540/NCU01540-uniprot.txt] “DR InterPro; IPR004680; Cit_transptr-like_dom.”

Provenance: live API snapshot 2026-09-09T03:00:51.831347+00:00. Complete API prediction JSON and all emitted claim IDs, text, and original evidence are preserved in the source and provenance JSON files. Current sequence/annotation data are separate comparison snapshots. Annotation overlap records known biology, not demonstrated training membership. All seven gene-focused Falcon jobs completed; the provider reports were inspected and useful primary leads checked. Publication retrieval used Europe PMC metadata/XML when the canonical PubMed fetch returned HTTP 429.