2001
Gene or accession: CG12286 and karmoisin
Release: 2
Missed gene
Comments: karmoisin is CG12286
karmoisin is a late-acting gene in the xanthommatin eye pigment pathway.
It has tentatively been assigned a role as phenoxazizone synthetase,
catalysing the bimolecular condensation of 3-hydroxykynurenine to the pigment
xanthommatin:
see gene report for kar:
'Phenoxazinone synthetase level subnormal in mutants; maybe a structural gene
for this enzyme; 3-hydroxykynurenine accumulates (Sullivan, Kitos and
Sullivan, 1974).'
However, the only Blast matches for Streptomyces antibioticus Phenoxazizone
synthase (AAA86668) are multicopper oxidases at 16D6 and 96F8.
In cloning and rescuing Su(fu), Pham et al., 1995
('The suppressor of fused gene encodes a novel PEST protein involved in
Drosophila segment polarity establishment. Genetics 140(2): 587--598
<up>FBrf0082477</up>') showed that kar is rescued by the 4kb immediately downstream
of Su(fu), and provisionally worked out some of the exons of kar, which was in
the same orientation.
With the benefit of the genome project, we can see that the only ORF and EST
hit in this region is CG12286. This has been identified by Gadfly and my
searches as a monocarboylic acid transporter (solute carrier family 16).
I believe the work by Pham
(http://fly.ebi.ac. uk:7081 /.bin/molmap.html?FBgn0001296) is sufficient to
identify this gene unambiguously.
Interestingly, 3-hydroxykynurenine IS a monocarboxylic acid
(http://www.genome.ad.jp/dbget-bin/www_bget?compound+C03277).
I therefore propose that kar is the transporter responsible for getting
3-hydroxykynurenine to its target site, where another enzyme catalyses the
condensation to xanthommatin.
Consistent with this, CG12286 is very heavily represented in the RH (head) EST
sequences released in August 2001.
Does kar act to import 3-hydroxykynurenine at the plasma membrane, or into
vesicles? A Psort II prediction with the Gadfly predicted peptide suggests
that this is plasma membrane:
>k = 9/23
> 69.6 %: plasma membrane
> 21.7 %: endoplasmic reticulum
> 4.3 %: mitochondrial
> 4.3 %: nuclear
>
>>> prediction for QUERY is pla (k=23)