Abstract
The plant cell wall hemicellulose xyloglucan in most dicot species consists of repeating units of three consecutive xylosylated Glc residues followed by an unsubstituted Glc (XXXG). Available evidence suggests that galactosylation of the second and the third Xyl side chains of XXXG is carried out regiospecifically by two xyloglucan galactosyltransferases XLT2 and MUR3, respectively, resulting in XLXG and XXLG units, but the mechanism underlying their regiospecificity remains elusive. In this report, we demonstrated that recombinant MUR3 and XLT2 proteins of Arabidopsis, poplar and duckweed were able to regiospecifically galactosylate not only XXXG, but also XLXG and XXLG, respectively, to generate XLLG. Interestingly, they were also able to galactosylate mono- and di-xylosylated xyloglucan oligomers. Protein structural modeling revealed that Arabidopsis and poplar MUR3 proteins contained an α-helical lid-like domain covering their active site clefts and its deletion led to increased galactosyltransferase activity. Molecular docking of the structural models of MUR3 and XLT2 identified amino acid residues interacting with UDP-Gal and XXXG in their active site clefts. Furthermore, site-directed mutagenesis uncovered critical roles of these substrate-interacting residues in the catalytic activity. Together, these findings provide biochemical insights into the molecular determinants of the regiospecificity of MUR3 and XLT2 in xyloglucan galactosylation.
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Claims 6
Claim · model-written summary
MUR3 and XLT2 regiospecifically galactosylated XXXG, XLXG and XXLG to yield XLLG.
- Taxon
- Arabidopsis, poplar and duckweed
Populus
Arabidopsis
Lemnae0 - Gene
- MUR3 and XLT2e0
- Outcome
- regiospecifically galactosylate not only XXXG, but also XLXG and XXLGe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“recombinant MUR3 and XLT2 proteins of Arabidopsis, poplar and duckweed were able to regiospecifically galactosylate not only XXXG, but also XLXG and XXLG, respectively, to generate XLLG”
Claim · model-written summary
The proteins also galactosylated mono- and di-xylosylated xyloglucan oligomers.
- Taxon
- Arabidopsis, poplar and duckweedPopulusArabidopsisLemnae0
- Gene
- MUR3 and XLT2e0
- Outcome
- galactosylate mono- and di-xylosylated xyloglucan oligomerse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“recombinant MUR3 and XLT2 proteins of Arabidopsis, poplar and duckweed were able to regiospecifically galactosylate not only XXXG, but also XLXG and XXLG, respectively, to generate XLLG. Interestingly, they were also able to galactosylate mono- and di-xylosylated xyloglucan oligomers”
Claim · model-written summary
Arabidopsis and poplar MUR3 proteins had an α-helical lid-like domain over their active site clefts.
- Taxon
- Arabidopsis and poplarPopulusArabidopsise0
- Gene
- MUR3e0
- Outcome
- α-helical lid-like domain covering their active site cleftse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis and poplar MUR3 proteins contained an α-helical lid-like domain covering their active site clefts”
Claim · model-written summary
Deleting the lid-like domain increased galactosyltransferase activity.
- Taxon
- Arabidopsis and poplarPopulusArabidopsist0
- Treatment
- deletione0
- Outcome
- galactosyltransferase activitye0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“its deletion led to increased galactosyltransferase activity”
t0“Arabidopsis and poplar MUR3 proteins”
Claim · model-written summary
Docking identified residues that interact with UDP-Gal and XXXG.
- Taxon
- Arabidopsis and poplarPopulusArabidopsist0
- Gene
- MUR3 and XLT2e0
- Outcome
- amino acid residues interacting with UDP-Gal and XXXGe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Molecular docking of the structural models of MUR3 and XLT2 identified amino acid residues interacting with UDP-Gal and XXXG in their active site clefts”
t0“Arabidopsis and poplar MUR3 proteins”
Claim · model-written summary
Mutagenesis found substrate-interacting residues critical for catalytic activity.
- Taxon
- Arabidopsis and poplarPopulusArabidopsist0
- Outcome
- critical roles of these substrate-interacting residues in the catalytic activitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“site-directed mutagenesis uncovered critical roles of these substrate-interacting residues in the catalytic activity”
t0“Arabidopsis and poplar MUR3 proteins”