TY - JOUR
T1 - Molecular Mechanism of Polysaccharide Acetylation by the Arabidopsis Xylan O-acetyltransferase XOAT1
AU - Lunin, Vladimir
AU - Wang, Hsin-Tzu
AU - Bharadwaj, Vivek
AU - Alahuhta, Markus
AU - Pena, Maria
AU - Yang, Jeong-Yeh
AU - Archer-Hartmann, Stephanie
AU - Azadi, Parastoo
AU - Himmel, Michael
AU - Moremen, Kelley
AU - York, William
AU - Bomble, Yannick
AU - Urbanowicz, Breeanna
N1 - Publisher Copyright:
© 2020 ASPB.
PY - 2020/7
Y1 - 2020/7
N2 - Xylans are a major component of plant cell walls. O-Acetyl moieties are the dominant backbone substituents of glucuronoxylan in dicots and play a major role in the polymer-polymer interactions that are crucial for wall architecture and normal plant development. Here, we describe the biochemical, structural, and mechanistic characterization of Arabidopsis (Arabidopsis thaliana) xylan O-acetyltransferase 1 (XOAT1), a member of the plant-specific Trichome Birefringence Like (TBL) family. Detailed characterization of XOAT1-catalyzed reactions by real-time NMR confirms that it exclusively catalyzes the 2-O-acetylation of xylan, followed by nonenzymatic acetyl migration to the O-3 position, resulting in products that are monoacetylated at both O-2 and O-3 positions. In addition, we report the crystal structure of the catalytic domain of XOAT1, which adopts a unique conformation that bears some similarities to the a/b/a topology of members of the GDSL-like lipase/acylhydrolase family. Finally, we use a combination of biochemical analyses, mutagenesis, and molecular simulations to show that XOAT1 catalyzes xylan acetylation through formation of an acyl-enzyme intermediate, Ac–Ser-216, by a double displacement bi-bi mechanism involving a Ser-His-Asp catalytic triad and unconventionally uses an Arg residue in the formation of an oxyanion hole.
AB - Xylans are a major component of plant cell walls. O-Acetyl moieties are the dominant backbone substituents of glucuronoxylan in dicots and play a major role in the polymer-polymer interactions that are crucial for wall architecture and normal plant development. Here, we describe the biochemical, structural, and mechanistic characterization of Arabidopsis (Arabidopsis thaliana) xylan O-acetyltransferase 1 (XOAT1), a member of the plant-specific Trichome Birefringence Like (TBL) family. Detailed characterization of XOAT1-catalyzed reactions by real-time NMR confirms that it exclusively catalyzes the 2-O-acetylation of xylan, followed by nonenzymatic acetyl migration to the O-3 position, resulting in products that are monoacetylated at both O-2 and O-3 positions. In addition, we report the crystal structure of the catalytic domain of XOAT1, which adopts a unique conformation that bears some similarities to the a/b/a topology of members of the GDSL-like lipase/acylhydrolase family. Finally, we use a combination of biochemical analyses, mutagenesis, and molecular simulations to show that XOAT1 catalyzes xylan acetylation through formation of an acyl-enzyme intermediate, Ac–Ser-216, by a double displacement bi-bi mechanism involving a Ser-His-Asp catalytic triad and unconventionally uses an Arg residue in the formation of an oxyanion hole.
KW - acetylation
KW - acetyltransferase
KW - hemicellulose
KW - xylans
UR - http://www.scopus.com/inward/record.url?scp=85089059479&partnerID=8YFLogxK
U2 - 10.1105/tpc.20.00028
DO - 10.1105/tpc.20.00028
M3 - Article
C2 - 32354790
AN - SCOPUS:85089059479
SN - 1040-4651
VL - 32
SP - 2367
EP - 2382
JO - Plant Cell
JF - Plant Cell
IS - 7
ER -