NTR: sulfite export across plasma membrane

[ValWood]

Please provide as much information as you can:

• Suggested term label:

sulfite export across plasma membrane

• Definition (free text)
  The directed movement of sulfite from inside of a cell, across the plasma membrane and into the extracellular region.

• Reference, in format PMID:#######

PMID: 17322211
PMID: 30859719
The most efficient sulfite detoxification mechanism in Saccharomyces cerevisiae uses a plasma membrane protein called Ssu1 to efflux sulfite.

• Gene product name and ID to be annotated to this term

https://www.pombase.org/gene/SPBPB10D8.04c

• Parent term(s)

GO:0000316 sulfite transmembrane transport

• Synonyms (please specify, EXACT, BROAD, NARROW or RELATED)

sulfite efflux

• Any other information

[raymond91125]

"SSU1 encodes a sulphite efflux pump" @ValWood Would it be better if we make this an MF (sulfite efflux transmembrane transporter activity), PART_OF sulfite detoxification (BP)?

[ValWood]

I thought the 'rule' for transporters is to encode the directionality of transport in the BP term and not in the MF term.
but I see we do have efflux pumps so this might be OK.

@pgaudet can confirm.

[ValWood]

we have many terms with "export across the plasma membrane" (and many children)

[raymond91125]

we have many terms with "export across the plasma membrane" (and many children)

Yes. But I thought in the case of SSU1, it's a single step process.

[deustp01]

I thought the 'rule' for transporters is to encode the directionality of transport in the BP term and not in the MF term.

Is there also a need for a distinction between pumps (movement of specific chemical entities in a direction determined by the orientation of the energy-consuming pump in the membrane) and channels (movement of specific chemical entities down a concentration gradient determined by the relative concentrations of the entities on the two sides of the membrane)?

[ValWood]

• I don't know if the sulphite efflux family are channels or pumps. This doesn't appear to be annotated. They are Major Facilitator Superfamily so they could be channels or pumps.

• I wanted to describe the direction, because I wanted to make it clear in my model for sulphur assimilation that sulfite was exported, not imported.

• I can't remember whether the correct way to model direction is by MF or BP, but historically we have BP for transmembrane transport of substrates, because, in most cases multiple transporters with different affinities contribute to a BP. I'm not sure if this is the best way to model TM transport long term, or whether transporters should be integrated in some way with metabolism. I have a future question about this for the Noctua modelling call (low priority)