gocentral
commented
18 years ago Logged In: YES user_id=436423
From the intro to PMID 12486120, I'm getting the idea that GO:0008262 isn't meant for importin alpha itself, but for the 'receptor' that brings importin alpha back to the cytoplasm.
Admittedly, there is still a gene product (Cse1p/CAS), but at least what it does can be described, e.g.
'Interacting selectively with importin alpha and catalyzing its transfer across the nuclear envelope to the cytoplasm.'
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Original comment by: mah11
GO:0008262 : importin-alpha export receptor activity
This GO term refers to a gene product.
Importins (also known as karyopherins)
It should probably be merged with protein carrier activity (which seems to be used to annotate karyopherins?), and curators should also be referred to teh appropriate 'binding ' terms for NLS/NES
In fact, karyopherins porbably mediate a number of molecular functions (NLS/NES substrate binding, docking, transport...)
see below from
http://eurekah.com/abstract.php?chapid=616&bookid=55&catid=15&PHPSESSID=5d8c1efe1521011a80d0efa7239ecd77
.....and intracellular receptor molecules of the importin/karyopherin superfamily which recognise and dock the nuclear import substrates carrying these signals at the nuclear pore. Subsequent to translocation through the pore via a series of importin-mediated docking steps at multiple sites within it, release into the nucleus is effected by the monomeric guanine nucleotide binding protein Ran. Different importins possess distinct target sequence-binding specificities, meaning that different importins mediate the nuclear import of different classes of proteins. This extends to different classes of transcription factors which are recognised by distinct importins, and whose transport to the nucleus is modulated by specific regulatory mechanisms. The first step of nuclear import is of central importance, with the affinity of the importin:targeting signal interaction being a critical parameter in determining transport efficiency. In the whole cell context, target signal recognition can be modulated through differential expression of the importins themselves, as well as through competition between different importins for the same nuclear import substrate, and between different nuclear import substrates for the same importin. In addition, there are specific mechanisms to modulate targeting sequence-importin interaction directly through phosphorylation. The fact that there are distinct nuclear import pathways for different types of nuclear import substrates enables the cell to regulate these pathways specifically, ensuring efficient nuclear import of particular proteins as and when required.
Reported by: ValWood
Original Ticket: "geneontology/ontology-requests/3267":https://sourceforge.net/p/geneontology/ontology-requests/3267