Ferredoxin-dependent glutamate synthase moonlights in plant sulfolipid biosynthesis by forming a complex with SQD1.
UDP-sulfoquinovose synthase, SQD1, catalyzes the transfer of sulfite to UDP-glucose giving rise to UDP-sulfoquinovose, which is the head group donor for the biosynthesis of the plant sulfolipid sulfoquinovosyldiacylglyerol. The native SQD1 enzyme of spinach exists as a 250 kDa heteroprotein complex with much higher affinity for the substrate sulfite than the recombinant SQD1 protein itself. The SQD1 protein co-purified with nine proteins. Likely binding partners included rubisco activase, HSP70, and ferredoxin-dependent glutamate synthase (FdGOGAT). While the first two proteins are known to interact with many other proteins, the identification of FdGOGAT was most intriguing because this 160kDa protein contains an FMN cofactor known to bind sulfite in vitro. Using different constructs expressing recombinant forms of the multidomain protein FdGOGAT, it was demonstrated that the FMN-binding domain of FdGOGAT is essential for specific binding of the protein to SQD1. A model suggests that FdGOGAT could channel sulfite to SQD1.
Shimojima
Mie
M
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824- 1319, USA.
Hoffmann-Benning
Susanne
S
Garavito
R Michael
RM
Benning
Christoph
C
D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D005288:Ferredoxins / Q000378:metabolism*; D005964:Glucosyltransferases / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018724:Spinacia oleracea / Q000378:metabolism*; D013379:Substrate Specificity
D029681:Arabidopsis Proteins; D005288:Ferredoxins; D008055:Lipids; D011994:Recombinant Proteins; C110849:SQD1 protein, Arabidopsis; C015518:sulfolipids; D000594:Amino Acid Oxidoreductases; C042233:glutamate synthase (ferredoxin); D005964:Glucosyltransferases