glt-1: biological evidence

GLT-1 is a major facilitator superfamily glucose transporter that supplies low-affinity, high-capacity glucose uptake in Neurospora crassa. It is the system I component of the dual-affinity glucose uptake machinery and operates principally when glucose is abundant. Its plasma-membrane role follows from extracellular glucose uptake; the system I mechanism is described as facilitated diffusion. Glucose transport is directly demonstrated, whereas a dedicated glucose-sensing role is established for the separate HGT transporters.

• carbohydrate:proton symporter activity: GLT-1 directly transports D-glucose. The gene-level system I assignment and its published diffusion mechanism do not support transferring the proton-coupled mechanism of system II; use the demonstrated substrate-specific transporter term.
• carbohydrate transport: The radiolabeled uptake and complementation experiments establish D-glucose transport. The substrate-specific transmembrane process is more informative than this broad transport annotation.
• membrane: A multipass MFS transporter mediating uptake of extracellular glucose is functionally located at the plasma membrane. This is a physiological localization inference from uptake experiments, not a claimed native microscopy measurement.
• transmembrane transporter activity: The substrate is experimentally resolved as D-glucose, so the generic transporter activity can be made substrate-specific.
• carbohydrate transmembrane transport: The radiolabeled uptake and complementation experiments establish D-glucose transport. The substrate-specific transmembrane process is more informative than this broad transport annotation.
• transmembrane transport: The radiolabeled uptake and complementation experiments establish D-glucose transport. The substrate-specific transmembrane process is more informative than this broad transport annotation.
• proton transmembrane transport: GLT-1 is assigned to the low-affinity system I described as glucose diffusion, whereas proton cotransport describes system II. A proton-transport annotation overstates the established mechanism for this target.

Primary evidence excerpts

• PMID:24581151 “We conclude that NCU01633 is a D-glucose transporter of N. crassa, which was therefore named as D-glucose transporter 1 (GLT-1).”
• PMID:28115989 “system I is a glucose diffusion system, while system II is an active, H+-co-transport mechanism;”

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.

2026-09-20 full-gene reassessment

All eight rows and both primary full texts were assessed. PMID:24581151 heterologous expression/uptake identifies NCU01633 as GLT-1. PMID:28115989 Figures 2-5 and Methods directly address expression, glucose kinetics, mutants, complementation and eGFP localization (in yeast and Neurospora). The Discussion explicitly says “system I is a glucose diffusion system, while system II is an active, H+-co-transport mechanism”; GLT-1 is mapped to system I from kinetics/expression. These are substantive positive reasons to question coupling, but not a direct GLT-1 proton-flux assay. The Falcon report's evidence table similarly treats facilitated diffusion as less certain than glucose uptake.

Actual PTHR48022 tree places Q1K4S3 leaf PTN002362095 below PTN000627328, which bears membrane, carbohydrate transport and carbohydrate-proton symport IBDs. No negation is present in the recovered lineage. Broad transport/location terms are ACCEPT; coupling and its logical proton-transport derivative are UNDECIDED pending the focused report. The global OpenScientist GLT-1 hit concerns mammalian glutamate transport in Huntington disease and is not relevant to this fungal protein. No NEW assertion is necessary.