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

Shifra Lansky, Onit Alalouf, Vered Solomon, Anat Alhassid, Lata Govada, Naomi E. Chayan, Hassan Belrhali, Yuval Shoham*, Gil Shoham

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


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 from Geobacillus stearothermophilus T-6 has recently been cloned, overexpressed, purified, biochemically characterized and crystallized. One of the crystal forms obtained (RB1) belonged to the tetragonal space group I422, with unit-cell parameters a = 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.

Original languageAmerican English
Pages (from-to)430-434
Number of pages5
JournalActa Crystallographica Section F: Structural Biology and Crystallization Communications
Issue number4
StatePublished - Apr 2013


  • Geobacillus stearothermophilus
  • SAD data collection
  • selenium absorption edge
  • serine esterases
  • xylan esterases


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