Molecular Mechanism of Polysaccharide Acetylation by the Arabidopsis Xylan <i>O</i> -acetyltransferase XOAT1
V.V. Lunin, Hsin‐Tzu Wang, Vivek S. Bharadwaj, Markus Alahuhta, María J. Peña, Jeong‐Yeh Yang, Stephanie Archer‐Hartmann, Parastoo Azadi, Michael E. Himmel, Kelley W. Moremen, William S. York, Yannick J. Bomble, Breeanna R. Urbanowicz
Abstract
-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 α/β/α 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.