Crystallization and preliminary X-ray crystallographic analysis of a putative acetylxylan esterase fromTalaromyces cellulolyticus

Acetylxylan esterase (AXE) catalyzes the hydrolytic cleavage of the ester bond between acetic acid and hemicellulose in plant cell walls. A putative AXE gene exhibiting high homology to carbohydrate esterase family 3 was found in the genome database of the fungusTalaromyces cellulolyticus(formerly known asAcremonium cellulolyticus). A truncated form of the protein, the catalytic domain of the enzyme, was prepared and crystallized. The best crystal was obtained at 293 K using 0.17 Mammonium sulfate, 28% PEG 4000, 5%(v/v) glycerol, 0.5%(w/v)n-octyl-β-D-glucoside. X-ray diffraction data were collected to 1.50 Å resolution. The crystal belonged to space groupP41212 orP43212, with unit-cell parametersa= 70.90,b= 70.90,c= 87.09 Å. One enzyme molecule per asymmetric unit gave a crystal volume per protein mass (VM) of 2.62 Å3 Da−1and a solvent content of 53.0%(v/v).

Crystallization and preliminary crystallographic analysis of Axe2, an acetylxylan esterase fromGeobacillus stearothermophilus. Corrigendum

The article by Lanskyet al.[(2013),Acta Cryst.F69, 430–434] is corrected.

Crystallization and preliminary crystallographic analysis of Axe2, an acetylxylan esterase fromGeobacillus stearothermophilus

Acetylxylan esterases are part of the hemi-cellulolytic system of many microorganisms which utilize plant biomass for growth. Xylans, which are polymeric sugars that constitute a significant part of the plant biomass, are usually substituted with acetyl side groups attached at position 2 or 3 of the xylose backbone units. Acetylxylan esterases hydrolyse the ester linkages of the xylan acetyl groups and thus improve the ability of main-chain hydrolysing enzymes to break down the sugar backbone units. As such, these enzymes play an important part in the hemi-cellulolytic utilization system of many microorganisms that use plant biomass for growth. Interest in the biochemical characterization and structural analysis of these enzymes stems from their numerous potential biotechnological applications. An acetylxylan esterase (Axe2) of this type fromGeobacillus stearothermophilusT-6 has recently been cloned, overexpressed, purified, biochemically characterized and crystallized. One of the crystal forms obtained (RB1) belonged to the tetragonal space groupI422, with unit-cell parametersa=b= 110.2,c= 213.1 Å. A full diffraction data set was collected to 1.85 Å resolution from flash-cooled crystals of the wild-type enzyme at 100 K using synchrotron radiation. A selenomethionine derivative of Axe2 has also been prepared and crystallized for single-wavelength anomalous diffraction experiments. The crystals of the selenomethionine-derivatized Axe2 appeared to be isomorphous to those of the wild-type enzyme and enabled the measurement of a full 1.85 Å resolution diffraction data set at the selenium absorption edge and a full 1.70 Å resolution data set at a remote wavelength. These data are currently being used for three-dimensional structure determination of the Axe2 protein.

Cloning, Overexpression in Escherichia coli, and Characterization of a Thermostable Fungal Acetylxylan Esterase from Talaromyces emersonii

ABSTRACTThe gene encoding an acetylxylan esterase (AXE1) from the thermophilic ascomyceteTalaromyces emersoniiwas cloned, expressed inEscherichia coli, and characterized. This form of AXE1, rTeAXE1, exhibits increased thermostability and activity at a higher temperature than other known fungal acetyl esterases, thus having huge potential application in biomass bioconversion to high value chemicals or biofuels.